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Influenza vaccines administered as intramuscularly injected inactivated viruses or intranasally administered live-attenuated viruses usually provide short-term protection against influenza infections. Biodegradable particles that provide sustained release of the antigen has been studied as an approach to extend vaccine protection. Here, we investigate sustained release of ultraviolet killed influenza A virus (A/PR/8/34(H1N1)) (kPR8) loaded into poly(D,L-lactic-co-glycolic acid) (PLGA) microparticles. Particles were prepared using the double emulsion method, and polymer molecular weight (MW), polymer hydrophobicity, polymer concentration in the organic phase, and the amount of killed virus were varied to obtain a range of particles. Formulations included PLGA 50:50 (2-6, 7-17 kDa), PLGA 75:25 (4-15 kDa), and 50/50 PLGA 75:25 (4-15 kDa)/PCL (14 kDa). Additionally, NaOH was co-encapsulated in some cases to enhance particle degradation. The structure of the particles was explored by size measurements and electron microscopy. The kPR8 release profiles were measured using hemagglutinin ELISA. The concentration of the polymer (PLGA) in the organic phase and polymer MW significantly influenced virus loading, while polymer MW and co-encapsulation of NaOH modulated the release profiles. Mice receiving a single intramuscular injection of NaOH microparticle-encapsulated kPR8 were partially protected against a lethal influenza challenge 32 weeks post immunization. Microparticle (MP) vaccination induced a gradual increase in PR8-specific IgGs dominated by IgG1 in contrast to the rapid IgG2a-biased response elicited by soluble kPR8 immunization. Our results indicate that vaccine-NaOH co-loaded PLGA particles show potential as a single dose vaccination strategy for extended protection against influenza virus infection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Epizootic haemorrhagic disease (EHD), caused by the EHD virus (EHDV), is a vector-borne viral disease transmitted through Culicoides biting midges. EHDV comprises seven serotypes (1, 2, and 4-8), with EHDV-8 having recently emerged and spread in Europe over the last two years. Such event has raised concerns about the significant threat posed by EHDV-8 to livestock industry. In this study, an inactivated vaccine against EHDV-8 (vEHDV8-IZSAM) was developed. Safety and efficacy of the vaccine were evaluated in calves through clinical, serological, and virological monitoring following experimental challenge. The vaccine was proven safe, with only transient fever and localized reactions observed in a few animals, consistent with adjuvanted vaccine side effects. vEHDV8-IZSAM elicited a robust humoral response, as evidenced by the presence of neutralizing antibodies. After challenge with a virulent isolate, viraemia and clinical signs were evidenced in control animals but in none of the vaccinated animals. This study highlights the potential of vEHDV8-IZSAM as a safe and highly effective vaccine against EHDV-8 in cattle. It offers protection from clinical disease and effectively prevents viraemia. With the recent spread of EHDV-8 in European livestock, the use of an inactivated vaccine could be key in protecting animals from clinical disease and thus to mitigate the economic impact of the disease. Further investigations are warranted to assess the duration of the induced immunity and the applicability of this vaccine in real-world settings. Accordingly, joint efforts between public veterinary institutions and pharmaceutical companies are recommended to scale up vaccine production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the IZSAM., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Influenza vaccination may protect through the humoral immune response, cellular immune response, or possibly both. Immunity after vaccination can be mediated through antibodies that may be detected by the rise of serum hemagglutination inhibition (HAI) titers. Our objective was to investigate the proportion of protection against influenza mediated through antibodies by measuring the rise of HAI titer (indirect effect) compared to that induced through other immune mechanisms (direct effect) for influenza A and B., Methods: We analysed data from a cluster randomized trial conducted during the 2008-2009 season in which Canadian Hutterite children were vaccinated against influenza. We used inverse probability weighting to calculate the indirect and direct effect of vaccination against influenza A/H3N2 and influenza B/Brisbane using HAI titres and overall vaccine efficacy., Results: We included data on 617 children from 46 Hutterite colonies, aged between 3 and 15 years who were vaccinated with either inactivated trivalent influenza vaccine or hepatitis A vaccine. Vaccine efficacy was 63 % for influenza A (H3N2) and 28 % for influenza B. The hazard ratio for protection against influenza A/H3N2 due to an indirect effect of vaccination was 0.96 (95 % confidence interval (CI) of 0.00 to 2.89) while for the direct effect it was 0.38 (95 % CI of 0.00 to 5.47). The hazard ratio for influenza B indirect effect was 0.75 (95 % CI of 0.07 to 1) and for the direct effect 0.96 (95 % CI of 0.00 to 12.02). In contrast, repeating the analysis using microneutralization in a subgroup of 488 children revealed that the protective effect for vaccination for A/H3N2 was entirely mediated by antibodies but only for 13 % for influenza B., Conclusions: Although vaccination provided higher protective effectiveness against influenza A than B, most of the influenza A vaccine efficacy likely occurred through antibodies other than what could be detected by HAI titres. In contrast, for influenza B, while the HAI titres appeared to mediate most of the vaccine effectiveness, this was not confirmed by microneutralization analysis., Competing Interests: Declaration of competing interest Dr. Loeb reports grant support from the Canadian Institutes of Health Research and WHO; receipt of an in-kind supply of vaccines from Sanofi; consulting fees for participation on advisory boards for Medicago, Novavax, Janssen, Pfizer, GSK, Merck, Sanofi, and Seqirus; and participation on a data and safety monitoring board for CanSino Biologics., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: This study was to assess the lot-to-lot consistency, immunogenicity and safety of three manufacturing lots of a quadrivalent inactivated influenza vaccine (IIV4)., Methods: A randomized, double-blind, phase IV clinical trial was conducted in healthy children, adolescents and adults aged 9-59 years in Guizhou Province, China. Eligible participants were enrolled and randomized into three groups in a ratio of 1:1:1 to receive a single dose of one of three manufacturing lots of IIV4. Serum samples were collected before and 28 days after vaccination for hemagglutination inhibition (HI) antibody testing. Safety data were collected for up to 28 days after vaccination. The primary objective was to evaluate the lot-to-lot consistency of immune response as assessed by the geometric mean titer (GMT) of HI antibody at 28 days after vaccination., Results: Between November 27, 2022 and December 18, 2022, 1260 eligible participants were enrolled, with similar participant demographics among groups. Immune responses after vaccination were comparable across groups, with the 95% confidence intervals (CIs) of GMT ratios for all 4 strains falling into the equivalence criterion of (0.67, 1.5). The seroconversion rates (SCRs) and seroprotection rates (SPRs) met the US Center or Biologics Evaluation and Research (CBER) criteria for all strains for each lot (lower limit of 95% CI of SCR ≥ 40% and SPR ≥ 70%). The incidences of solicited and unsolicited adverse reactions were similar among three groups, most of which (91.9%) were mild or moderate in severity. A total of 11 serious adverse events were reported during the study, and all were considered unrelated to vaccination., Conclusion: The three manufacturing lots of IIV4 demonstrated consistent immunogenicity. IIV4 can elicit satisfactory immune responses for all four strains and no safety concerns were identified., Clinical Trial Registration: Identifier No. NCT05512494., Competing Interests: Declaration of competing interest Yuwei Li, Danyu and Jieru Wang are employed by Sinovac Biotech Co., Ltd. Xinyi Yang, and Siliang Zhou are employed by Sinovac Life Sciences Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Vaccines against influenza and many other infectious diseases require multiple boosters in addition to the primary dose to improve efficacy, but this approach is not ideal for compliance. The multiple doses could potentially be replaced by sustained or pulsatile release of antigens encapsulated in degradable microparticles (MPs). The efficacy of a vaccine is improved by adding an adjuvant, which can be co-delivered from the particles to enhance immunogenicity. Here, we developed degradable poly-lactic-co-glycolic acid (PLGA) (7-17 kDa) MPs capable of sustained release of ultraviolet killed influenza virus (A/PR/8/34) (kPR8) vaccine and the natural killer T (NKT) cell agonist alpha-galactosylceramide (α-GalCer) and tested their effectiveness at providing long-term protection against influenza virus infection in mice. Multiple formulations were developed for encapsulating the virus and adjuvant separately, and in combination. The MPs exhibited sustained release of both the virus and the adjuvant lasting more than a month. Co-encapsulation significantly increased the encapsulation efficiency (EE) of the vaccine but reduced the release duration. On the other hand, co-encapsulation led to a reduction in EE for the α-GalCer and a change in release profile to a higher initial burst followed by a linear release compared to a low initial burst and slower linear release. The α-GalCer also had considerably longer release duration compared to the vaccine. Mice injected with particle formulations co-encapsulating kPR8 and α-GalCer were protected from a lethal influenza virus infection 30 weeks after vaccination. This study demonstrates that PLGA MP based vaccines are promising for providing effective vaccination and possibly for replacing multiple doses with a single injection., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Inactivated whole-virus vaccination elicits immune responses to both SARS-CoV-2 nucleocapsid (N) and spike (S) proteins, like natural infections. A heterologous Ad26.COV2.S booster given at two different intervals after primary BBIBP-CorV vaccination was safe and immunogenic at days 28 and 84, with higher immune responses observed after the longer pre-boost interval. We describe booster-specific and hybrid immune responses over 1 year., Methods: This open-label phase 1/2 study was conducted in healthy Thai adults aged ≥ 18 years who had completed primary BBIBP-CorV primary vaccination between 90-240 (Arm A1; n = 361) or 45-75 days (Arm A2; n = 104) before enrolment. All received an Ad26.COV2.S booster. We measured anti-S and anti-N IgG antibodies by Elecsys®, neutralizing antibodies by SARS-CoV-2 pseudovirus neutralization assay, and T-cell responses by quantitative interferon (IFN)-γ release assay. Immune responses were evaluated in the baseline-seronegative population (pre-booster anti-N < 1.4 U/mL; n = 241) that included the booster-effect subgroup (anti-N < 1.4 U/mL at each visit) and the hybrid-immunity subgroup (anti-N ≥ 1.4 U/mL and/or SARS-CoV-2 infection, irrespective of receiving non-study COVID-19 boosters)., Results: In Arm A1 of the booster-effect subgroup, anti-S GMCs were 131-fold higher than baseline at day 336; neutralizing responses against ancestral SARS-CoV-2 were 5-fold higher than baseline at day 168; 4-fold against Omicron BA.2 at day 84. IFN-γ remained approximately 4-fold higher than baseline at days 168 and 336 in 18-59-year-olds. Booster-specific responses trended lower in Arm A2. In the hybrid-immunity subgroup at day 336, anti-S GMCs in A1 were 517-fold higher than baseline; neutralizing responses against ancestral SARS-CoV-2 and Omicron BA.2 were 28- and 31-fold higher, respectively, and IFN-γ was approximately 14-fold higher in 18-59-year-olds at day 336. Durable immune responses trended lower in ≥ 60-year-olds., Conclusion: A heterologous Ad26.COV2.S booster after primary BBIBP-CorV vaccination induced booster-specific immune responses detectable up to 1 year that were higher in participants with hybrid immunity., Clinical Trials Registration: NCT05109559., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: S.M., R.W., S.K., S.L., A.J., A.T., V.L., P.C., N.T., N.C. report no potential conflicts of interest. S.N. has received honoraria for lectures from GSK, Zuellig Pharma, Astra Zeneca, Novartis, Abbot, Sanofi, Organon and Takeda and has participated in advisory boards for GlaxoSmithKline and Takeda. J.K.L. and T.A.W. and received institutional funding from Mahidol University to support study conduct, and T.A.W. supported management of Data Safety Monitoring Board activities and meetings. J-L.E. has no competing interests to declare.. M.F.R. is an employee of Janssen Pharmaceuticals and holds restricted stock units in the company. C.L. is an employee of Janssen Pharmaceuticals. T.K.M. has received consulting fees from Janssen Pharmaceuticals. P.P. has received funding from Mahidol University and Johnson & Johnson for study support., (Copyright © 2024. Published by Elsevier Ltd.)

We conducted a phase I, randomized, double-blind, placebo-controlled trial including healthy adults in Sui County, Henan Province, China. Ninety-six adults were randomly assigned to one of three groups (high-dose, medium-dose, and low-dose) at a 3:1 ratio to receive one vaccine dose or placebo. Adverse events up to 28 days after each dose and serious adverse events up to 6 months after all doses were reported. Geometric mean titers and seroconversion rates were measured for anti-rotavirus neutralizing antibodies using microneutralization tests. The rates of total adverse events in the placebo group, low-dose group, medium-dose group, and high-dose group were 29.17 % (12.62 %-51.09 %), 12.50 % (2.66 %-32.36 %), 50.00 % (29.12 %-70.88 %), and 41.67 % (22.11 %-63.36 %), respectively, with no significant difference in the experimental groups compared with the placebo group. The results of the neutralizing antibody assay showed that in the adult group, the neutralizing antibody geometric mean titer at 28 days after full immunization in the low-dose group was 583.01 (95 % confidence interval [CI]: 447.12-760.20), that in the medium-dose group was 899.34 (95 % CI: 601.73-1344.14), and that in the high-dose group was 1055.24 (95 % CI: 876.28-1270.75). The GMT of serum-specific IgG at 28 days after full immunization in the low-dose group was 3444.26 (95 % CI: 2292.35-5175.02), that in the medium-dose group was 6888.55 (95 % CI: 4426.67-10719.6), and that in the high-dose group was 7511.99 (95 % CI: 3988.27-14149.0). The GMT of serum-specific IgA at 28 days after full immunization in the low-dose group was 2332.14 (95 % CI: 1538.82-3534.45), that in the medium-dose group was 4800.98 (95 % CI: 2986.64-7717.50), and that in the high-dose group was 3204.30 (95 % CI: 2175.66-4719.27). In terms of safety, adverse events were mainly Grades 1 and 2, indicating that the safety of the vaccine is within the acceptable range in the healthy adult population. Considering the GMT and positive transfer rate of neutralizing antibodies for the main immunogenicity endpoints in the experimental groups, it was initially observed that the high-dose group had higher levels of neutralizing antibodies than the medium- and low-dose groups in adults aged 18-49 years. This novel inactivated rotavirus vaccine was generally well-tolerated in adults, and the vaccine was immunogenic in adults (ClinicalTrials.gov number, NCT04626856)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A Newcastle disease virus (NDV)-vectored vaccine expressing clade 2.3.4.4b H5 Hemagglutinin was developed and assessed for efficacy against H5N1 highly pathogenic avian influenza (HPAI) in specific pathogen-free (SPF) chickens, broilers, and domestic ducks. In SPF chickens, the live recombinant NDV-vectored vaccine, rK148/22-H5, achieved complete survival against HPAI and NDV challenges and significantly reduced viral shedding. Notably, the live rK148/22-H5 vaccine conferred good clinical protection in broilers despite the presence of maternally derived antibodies. Good clinical protection was observed in domestic ducks, with decreased viral shedding. It demonstrated complete survival and reduced cloacal viral shedding when used as an inactivated vaccine from SPF chickens. The rK148/22-H5 vaccine is potentially a viable and supportive option for biosecurity measure, effectively protecting in chickens against the deadly clade 2.3.4.4b H5 HPAI and NDV infections. Furthermore, it aligns with the strategy of Differentiating Infected from Vaccinated Animals (DIVA)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: BBV152 (Covaxin™) is a whole-virion inactivated SARS-CoV-2 vaccine mixed with an immune adjuvant. We aimed to compare immune responses after booster vaccination with heterologous BBV152 versus homologous mRNA vaccine., Methods: We conducted a randomized, participant-blinded, controlled trial. Fifty mRNA-vaccinated participants were enrolled and randomized to receive an mRNA booster (n = 26) or BBV152 (n = 24). Blood samples were collected pre-vaccination, and at Day 7, 28, 180 and 360 post-booster for analysis of humoral and cellular immune responses. Primary end point was the SARS-CoV-2 anti-spike antibody titer at day 28., Results: Recruitment began in January 2022 and was terminated early due to the BBV152 group meeting pre-specified criteria for futility. At Day 28 post-boost, mean SARS-CoV-2 spike antibody titers were lower with BBV152 (2004 IU/mL; 95 % confidence interval [CI], 1132-3548) vs mRNA (26,669 IU/mL; 95 % CI, 21,330-33,266; p < 0.0001), but comparable levels of spike-specific CD4 and cytotoxic T-cells were observed. Anti-spike antibody titers remained significantly different at Day 180: BBV152 4467 IU/mL (95 % CI, 1959-10,186) vs mRNA 20,749 IU/mL (95 % CI, 12,303-35,075; p = 0.0017). Levels of surrogate virus neutralizing antibodies against ancestral and Omicron subvariants BA.1 and BA.2 were significantly higher among mRNA recipients at Day 180, including after adjusting for intercurrent infection. By Day 360, anti-spike antibody titers and neutralizing antibody levels against Omicron subvariants became similar between vaccine groups. By the end of the study, 16 in each arm (mRNA 64 % and BBV152 69.6 %) had breakthrough infections and time to COVID-19 infection between vaccine groups were similar (p = 0.63)., Conclusions: Wild-type SARS-CoV-2 anti-spike antibody titer and surrogate virus neutralizing test levels against wild-type SARS-CoV-2 and Omicron subvariants BA.1/BA.2/BA.5 were significantly higher at Day 28 and 180 in individuals who received booster vaccination with an mRNA vaccine compared with BBV152., Clinical Trial Registration Number: NCT05142319., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Mycoplasma (M.) hyopneumoniae is a primary etiological agent of porcine enzootic pneumonia (PEP), a disease that causes significant economic losses to pig farming worldwide. Current commercial M. hyopneumoniae vaccines induce partial protection, decline in preventing transmission of this pathogen or inducing complete immunity, evidencing the need for improving vaccines against PEP. In our study, we aimed to test the effectiveness of the SBA-15 ordered mesoporous silica nanostructured particles as an immune adjuvant of a vaccine composed of M. hyopneumoniae strain 232 proteins encapsulated in SBA-15 and administered by intramuscular route in piglets to evaluate the immune responses and immune-protection against challenge. Forty-eight 24-day-old M. hyopneumoniae-free piglets were divided into four experimental groups with different protocols, encompassing a commercial vaccine against M. hyopneumoniae, SBA-15 vaccine, SBA-15 adjuvant without antigens and a non-immunized group. All piglets were challenged with the virulent strain 232 of M. hyopneumoniae. Piglets that received the SBA-15 and commercial vaccine presented marked immune responses characterized by anti-M. hyopneumoniae IgA and IgG antibodies in serum, anti-M. hyopneumoniae IgA antibodies in nasal mucosa and showed an upregulation of IL-17 and IL-4 cytokines and downregulation of IFN-γ in lungs 35 days post-infection. Piglets immunized with SBA-15 vaccine presented a reduction of bacterial shedding compared to piglets immunized with a commercial bacterin. In addition, piglets from SBA-15 adjuvant suspension group presented increased IL-17 gene expression in the lungs without involvement of Th1 and Th2 responses after challenge. These results indicated that SBA-15 vaccine induced both humoral and cell-mediated responses in the upper respiratory tract and lungs, first site of replication and provided protection against M. hyopneumoniae infection with a homologous strain with reduction of lung lesions and bacterial shedding. Finally, these results enhance the potential use of new technologies such as nanostructured particles applied in vaccines for the pig farming industry., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Background: The annual administration of the influenza vaccine is the most effective method for preventing influenza. We have evaluated the effectiveness of the inactivated influenza vaccine in children aged 6 months to 15 years across the seasons from 2013/2014 to 2022/2023. This study aims to investigate the effectiveness of the inactivated influenza vaccine in the 2023/2024 season, the first year following the easing of strict COVID-19 measures, and possibly the last season when only the inactivated vaccine is available on the market., Methods: Adjusted vaccine effectiveness for the 2023/2024 season was assessed using a test-negative case-control design, with results based on polymerase chain reaction and rapid influenza diagnostic tests. Vaccine effectiveness was calculated by influenza type and patient hospitalization/outpatient status., Results: A total of 1832 children were recruited. The inactivated influenza vaccine was effective in preventing both symptomatic influenza A and B in both inpatient and outpatient settings. Overall vaccine effectiveness for influenza A was 51% (95% confidence interval [CI], 23%-69%, n = 930) in inpatient settings and 54% (95%CI, 27%-71%, n = 559) in outpatient settings. For influenza B, effectiveness was 60% (95%CI, 22%-79%, n = 859) in inpatient settings and 56% (95%CI, 26%-74%, n = 558) in outpatient settings. Analysis suggested that administering two doses enhanced effectiveness specifically against influenza B., Conclusions: This is the first study to demonstrate influenza vaccine effectiveness in children after the relaxation of strict COVID-19 measures in Japan (2023/2024). We recommend the current inactivated vaccine for preventing both influenza A and B in children, with consideration for the potential use of two doses to enhance effectiveness against influenza B., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Masayoshi Shinjoh (Shinjo) reports a relationship with MSD KK that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with Meiji Seika Pharma Co Ltd. that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with Mitsubishi Tanabe Pharma Corporation that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with KM Biologics Co Ltd. that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with Shionogi and Co Ltd. that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with DAIICHI SANKYO COMPANY, LIMITED that includes: speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with Takeda Pharmaceutical Company Limited that includes: consulting or advisory and speaking and lecture fees. Masayoshi Shinjoh (Shinjo) reports a relationship with Pfizer Japan Inc. that includes: consulting or advisory. Masayoshi Shinjoh (Shinjo) reports a relationship with Janssen Pharmaceutical KK that includes: consulting or advisory. Masayoshi Shinjoh (Shinjo) reports a relationship with Astellas Pharma Inc. that includes: consulting or advisory. This work was supported by JSPS KAKENHI, Japan (Grant Number JP20K10546). Outside this study, the corresponding author received Health Labour Sciences Research Grant, Japan (2024). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Novel coronaviruses constitute a significant health threat, prompting the adoption of vaccination as the primary preventive measure. However, current evaluations of immune response and vaccine efficacy are deemed inadequate., Objectives: The study sought to explore the evolving dynamics of immune response at various vaccination time points and during breakthrough infections. It aimed to elucidate the synergistic effects of epidemiological factors, humoral immunity, and cellular immunity. Additionally, regression curves were used to determine the correlation between the protective efficacy of the vaccine and the stimulated immune response., Methods: Employing LASSO for high-dimensional data analysis, the study utilised four machine learning algorithms-logistical regression, random forest, LGBM classifier, and AdaBoost classifier-to comprehensively assess the immune response following booster vaccination., Results: Neutralising antibody levels exhibited a rapid surge post-booster, escalating to 102.38 AU/mL at one week and peaking at 298.02 AU/mL at two weeks. Influential factors such as sex, age, disease history, and smoking status significantly impacted post-booster antibody levels. The study further constructed regression curves for neutralising antibodies, non-switched memory B cells, CD4 + T cells, and CD8 + T cells using LASSO combined with the random forest algorithm., Conclusion: The establishment of an artificial intelligence evaluation system emerges as pivotal for predicting breakthrough infection prognosis after the COVID-19 booster vaccination. This research underscores the intricate interplay between various components of immunity and external factors, elucidating key insights to enhance vaccine effectiveness. 3D modelling discerned distinctive interactions between humoral and cellular immunity within prognostic groups (Class 0-2). This underscores the critical role of the synergistic effect of humoral immunity, cellular immunity, and epidemiological factors in determining the protective efficacy of COVID-19 vaccines post-booster administration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Background: Previous research suggested that the inactivated influenza vaccine (IIV) may protect against SARS-CoV-2 infection or a severe course of COVID-19. These findings were however based on cohort studies, that are prone to confounding by indication. We examined the association between IIV and SARS-Cov-2 infection in a Dutch population using a test-negative design., Methods: This test-negative case-control study was conducted in adults (≥60) who tested because of COVID-19 like symptoms at community SARS-CoV-2 testing locations in the Netherlands during the period of November 8th 2021-March 11th 2022. Information on receipt of IIV in October-November 2021 was routinely collected at each visit. Logistic regression was used to calculate unadjusted, partially (sex, age, education level) and fully adjusted (COVID-19 vaccination, IIV 2020) odds ratios (ORs) for receipt of IIV in SARS-CoV-2 positive versus negative subjects. Differential effects on SARS-CoV-2 risk by time since IIV were investigated by including an interaction term for calendar time: November 2021-January 2022 vs February-March 2022., Results: In total, 1,832 participants were included in the main analysis, of whom 336 (18.3 %) had a positive SARS-CoV-2 test. No significant association between IIV and SARS-CoV-2 infection was found; fully adjusted OR of 1.07 (95 % CI: 0.78-1.49). The interaction term for time periods was not significant (1.04 [95 % CI: 0.51-2.15], p = 0.91). Results were robust in sensitivity analyses., Conclusions: While earlier observational studies suggested a protective non-specific effect of IIV and SARS-CoV-2 infections, this smaller, but well controlled test-negative design study does not suggest an effect, either positive or negative. Larger test-negative design studies, or alternative designs such as the self-controlled case series design are needed to confirm these findings and provide more definite answers on the topic., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier India Pvt Ltd. Published by Elsevier Ltd. All rights reserved.)

Leptospirosis, a globally significant zoonotic disease caused by pathogenic Leptospira, continues to threaten the health and public safety of both humans and animals. Current clinical treatment of leptospirosis mainly relies on antibiotics but their efficacy in severe cases is controversial. Passive immunization has a protective effect in the treatment of infectious diseases. In addition, chicken egg yolk antibody (IgY) has gained increasing attention as a safe passive immunization agent. This study aimed to investigate whether hens produce specific IgY after immunization with inactivated Leptospira and the protective effect of specific IgY against leptospirosis. First, it was demonstrated that specific IgY could be extracted from the eggs of hens vaccinated with inactivated Leptospira and that specific IgY can specifically recognize and bind homotypic Leptospira with a high titre, as shown by MAT and ELISA. Next, we tested the therapeutic effects of IgY in early and late leptospirosis using a hamster model. The results showed that early specific IgY treatment increased the survival rate of hamsters to 100%, alleviated pathological damage to the liver, kidney, and lung, reduced leptospiral burden, and restored haematological indices as well as functional indicators of the liver and kidney. The therapeutic effect of early specific IgY was comparable to that of doxycycline. Late IgY treatment also enhanced the survival rate of hamsters and improved the symptoms of leptospirosis similar to early IgY treatment. However, the therapeutic effect of late IgY treatment was better when combined with doxycycline. Furthermore, no Leptospira colonization was observed in the kidneys, livers, or lungs of the surviving hamsters treated with specific IgY. Mechanistically, IgY was found to inhibit the growth and adhesion to cells of Leptospira. In conclusion, passive immunotherapy with specific IgY can be considered an effective treatment for leptospirosis, and may replace antibiotics regarding its therapeutic effects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: A global shortage of cholera vaccines has increased the use of single-dose regimens, rather than the standard two-dose regimen. There is sparse evidence on single-dose protection, particularly in children. In 2020, a mass vaccination campaign was conducted in Uvira, an endemic urban setting in eastern Democratic Republic of the Congo, resulting in largely single-dose coverage. We examined the effectiveness of a single-dose of the oral cholera vaccine Euvichol-Plus in this high-burden setting., Methods: In this matched case-control study, we recruited individuals with medically attended confirmed cholera in the two cholera treatment facilities in the city of Uvira. The control group consisted of age-matched, sex-matched, and neighbourhood-matched community individuals. We recruited across two distinct periods: Oct 14, 2021, to March 10, 2022 (12-17 months after vaccination), and Nov 21, 2022, to Oct 18, 2023 (24-36 months after vaccination). Study staff administered structured questionnaires to all participants to capture demographics, household conditions, potential confounding variables, and vaccination status. The odds of vaccination for the case and control groups were contrasted in conditional logistic regression models to estimate unadjusted and adjusted vaccine effectiveness., Findings: We enrolled 658 individuals with confirmed cholera and 2274 matched individuals for the control group. 99 (15·1%) individuals in the case group were younger than 5 years at the time of vaccination. The adjusted single-dose vaccine effectiveness was 52·7% (95% CI 31·4 to 67·4) 12-17 months after vaccination and 44·7% (24·8 to 59·4) 24-36 months after vaccination. Although protection in the first 12-17 months after vaccination was similar for children aged 1-4 years and older individuals, the estimate of protection in children aged 1-4 years appeared to wane during the third year after vaccination (adjusted vaccine effectiveness 32·9%, 95% CI -30·7 to 65·5), with CIs spanning the null., Interpretation: A single dose of Euvichol-Plus provided substantial protection against medically attended cholera for at least 36 months after vaccination in this cholera-endemic setting. Although the evidence provides support for similar levels of protection in young children and others in the short term, protection among children younger than 5 years might wane significantly during the third year after vaccination., Funding: Wellcome Trust and Gavi, the Vaccine Alliance., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Background: Enterotoxigenic Escherichia coli (ETEC) is an important cause of moderate to severe diarrhoea in children for which there is no licensed vaccine. We evaluated ETVAX®, an oral, inactivated ETEC vaccine containing four E. coli strains over-expressing the major colonization factors CFA/I, CS3, CS5, and CS6, a toxoid (LCTBA) and double mutant heat-labile enterotoxin (dmLT) adjuvant for safety, tolerability, and immunogenicity., Methods: A double-blind, placebo-controlled, age-descending, dose-finding trial was undertaken in 40 adults, 60 children aged 10-23 months, and 146 aged 6-9 months. Adults received one full dose of ETVAX® and children received 3 doses of either 1/4 or 1/8 dose. Safety was evaluated as solicited and unsolicited events for 7 days following vaccination. Immunogenicity was assessed by evaluation of plasma IgA antibody responses to CFA/I, CS3, CS5, CS6, and LTB, and IgG responses to LTB., Results: Solicited adverse events were mostly mild or moderate with only 2 severe fever reports which were unrelated to the vaccine. The most common events were abdominal pain in adults (26.7 % in vaccinees vs 20 % in placebos), and fever in children aged 6-9 months (44 % vs 54  %). Dosage, number of vaccinations and decreasing age had no influence on severity or frequency of adverse events. The vaccine induced plasma IgA and IgG responses against LTB in 100 % of the adults and 80-90 % of the children. In the 6-23 months cohort, IgA responses to more than 3 vaccine antigens after 3 doses determined as ≥2-fold rise was significantly higher for 1/4 dose compared to placebo (56.7 % vs 27.2 %, p = 0.01). In the 6-9 months cohort, responses to the 1/4 dose were significantly higher than 1/8 dose after 3 rather than 2 doses., Conclusion: ETVAX® was safe, tolerable, and immunogenic in Zambian adults and children. The 1/4 dose induced significantly stronger IgA responses and is recommended for evaluation of protection in children., Clinical Trials Registration: The trial is registered with the Pan African Clinical Trials Registry (PACTR Ref. 201905764389804) and a description of this clinical trial is available on: https://pactr.samrc.ac.za/Trial Design., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Nils Carlin and Björn Sjöstrand are employees and minority shareholder of Scandinavian Biopharma Holding AB, which holds certain commercial rights to the vaccine tested in this study. Ann-Mari Svennerholm is shareholder of the biotech company Gotovax AB that may receive a small royalty on sales of the ETEC vaccine if it becomes a commercial product. Nils Carlin and Ann-Mari Svennerholm have patent PCT/EP2012/067598-PCT and PCT/EP2011/065784-PCT. All other authors declare that they have no conflicts of interest., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Although SARS-CoV-2 infection often causes milder symptoms in children and adolescents, young people might still play a key part in SARS-CoV-2 transmission. An efficacious vaccine for children and adolescents could therefore assist pandemic control. For further evaluation of the inactivated COVID-19 vaccine candidate BBIBP-CorV, we assessed the safety and immunogenicity of BBIBP-CorV in participants aged 3-17 years., Methods: A randomised, double-blind, controlled, phase 1/2 trial was done at Shangqiu City Liangyuan District Center for Disease Control and Prevention in Henan, China. In phases 1 and 2, healthy participants were stratified according to age (3-5 years, 6-12 years, or 13-17 years) and dose group. Individuals with a history of SARS-CoV-2 or SARS-CoV infection were excluded. All participants were randomly assigned, using stratified block randomisation (block size eight), to receive three doses of 2 μg, 4 μg, or 8 μg of vaccine or control (1:1:1:1) 28 days apart. The primary outcome, safety, was analysed in the safety set, which consisted of participants who had received at least one vaccination after being randomly assigned, and had any safety evaluation information. The secondary outcomes were geometric meant titre (GMT) of the neutralising antibody against infectious SARS-CoV-2 and were analysed based on the full analysis set. This study is registered with www.chictr.org.cn, ChiCTR2000032459, and is ongoing., Findings: Between Aug 14, 2020, and Sept 24, 2020, 445 participants were screened, and 288 eligible participants were randomly assigned to vaccine (n=216, 24 for each dose level [2/4/8 μg] in each of three age cohorts [3-5, 6-12, and 13-17 years]) or control (n=72, 24 for each age cohort [3-5, 6-12, and 13-17 years]) in phase 1. In phase 2, 810 participants were screened and 720 eligible participants were randomly assigned and allocated to vaccine (n=540, 60 for each dose level [2/4/8 μg] in each of three age cohorts [3-5, 6-12, and 13-17 years]) or control (n=180, 60 for each age cohort [3-5, 6-12, and 13-17 years]). The most common injection site adverse reaction was pain (ten [4%] 251 participants in all vaccination groups of the 3-5 years cohort; 23 [9·1%] of 252 participants in all vaccination groups and one [1·2%] of 84 in the control group of the 6-12 years cohort; 20 [7·9%] of 252 participants in all vaccination groups of the 13-17 years cohort). The most common systematic adverse reaction was fever (32 [12·7%] of 251 participants in all vaccination groups and six [7·1%] of 84 participants in the control group of the 3-5 years cohort; 13 [5·2%] of 252 participants in the vaccination groups and one [1·2%] of 84 in the control group of the 6-12 years cohort; 26 [10·3%] of 252 participants in all vaccination groups and eight [9·5%] of 84 in the control group of the 13-17 years cohort). Adverse reactions were mostly mild to moderate in severity. The neutralising antibody GMT against the SARS-CoV-2 virus ranged from 105·3 to 180·2 in the 3-5 years cohort, 84·1 to 168·6 in the 6-12 years cohort, and 88·0 to 155·7 in the 13-17 years cohort on day 28 after the second vaccination; and ranged from 143·5 to 224·4 in the 3-5 years cohort, 127 to 184·8 in the 6-12 years cohort, and 150·7 to 199 in the 13-17 years cohort on day 28 after the third vaccination., Interpretation: The inactivated COVID-19 vaccine BBIBP-CorV is safe and well tolerated at all tested dose levels in participants aged 3-17 years. BBIBP-CorV also elicited robust humoral responses against SARS-CoV-2 infection after two doses. Our findings support the use of a 4 μg dose and two-shot regimen BBIBP-CorV in phase 3 trials in the population younger than 18 years to further ascertain its safety and protection efficacy against COVID-19., Funding: National Program on Key Research Project of China, National Mega projects of China for Major Infectious Diseases, National Mega Projects of China for New Drug Creation, and Beijing Science and Technology Plan., Translation: For the Chinese translation of the abstract see Supplementary Materials section., Competing Interests: Declaration of interests XMY, YTZ, YKY, HW, WW, NL, XJZ, LD, YXZ, JZ, MM, YLQ, SHZ, JJC, QQL, HF, YX, and XTZ are employees of Beijing Institute of Biological Products, which developed the vaccine and funded the trial. All other authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Backgrounds: To date, the effects of SARS-CoV-2 vaccines on people living with HIV (PLWH) were mainly focused on messenger RNA (mRNA) and adenovirus vector-based vaccines, and little is known about the effects of inactivated virus-based vaccine. This study was designed to determine the effects of inactivated SARS-CoV-2 vaccines on PLWH., Methods: Twenty-four HIV-positive individuals and 24 healthy donors (HD) were respectively recruited from Malipo Country People's Hospital and community in Kunming city. Enumeration of lymphocyte and CD4 + CD45RO + memory T cells were evaluated by flow cytometry. Competitive ELISA was used to measure the level of Anti-SARS-CoV-2 neutralization antibody. Spearman or Pearson correlation analysis was used to analyze the relationship between laboratory indicators and neutralization antibodies in PLWH. T-cell responses (Th1, Th2, Th17, Treg) and intracellular expression of cytokines (IL-2 and TNF-α) in CD4 or CD8 were induced by spike protein in SARS-CoV-2 (SARS-2-S) and further measured by intracellular staining., Results: CD4, B cells, CD4 + CD45RO + memory T cells in peripheral blood of PLWH are dramatically decreased in comparison with HD. Importantly, PLWH display comparable neutralizing antibody positive rate to HD after inoculation with inactivated SARS-CoV-2 vaccine. However, PLWH showed weaker responses to vaccines exhibited by lower levels of neutralizing antibodies. Correlation analysis shows that this is possibly caused by low number of CD4 and B cells. Furthermore, SARS-2-S-induced Th2 and Th17 responses are also decreased in PLWH, while no influences on Treg and other cytokines (IL-2, TNF-α and IFN-γ) observed., Conclusions: PLWH and HD have comparable neutralizing antibodies positive rates, but PLWH display weaker responses to inactivated SARS-CoV-2 vaccines in magnitude, which suggests that a booster dose or dose adjustment are required for HIV-infected individuals, especially for those with lower counts of CD4 T and B cells., (Copyright © 2021. Published by Elsevier B.V.)

Background: A vaccine against SARS-CoV-2 for children and adolescents will play an important role in curbing the COVID-19 pandemic. Here we aimed to assess the safety, tolerability, and immunogenicity of a candidate COVID-19 vaccine, CoronaVac, containing inactivated SARS-CoV-2, in children and adolescents aged 3-17 years., Methods: We did a double-blind, randomised, controlled, phase 1/2 clinical trial of CoronaVac in healthy children and adolescents aged 3-17 years old at Hebei Provincial Center for Disease Control and Prevention in Zanhuang (Hebei, China). Individuals with SARS-CoV-2 exposure or infection history were excluded. Vaccine (in 0·5 mL aluminum hydroxide adjuvant) or aluminum hydroxide only (alum only, control) was given by intramuscular injection in two doses (day 0 and day 28). We did a phase 1 trial in 72 participants with an age de-escalation in three groups and dose-escalation in two blocks (1·5 μg or 3·0 μg per injection). Within each block, participants were randomly assigned (3:1) by means of block randomisation to receive CoronaVac or alum only. In phase 2, participants were randomly assigned (2:2:1) by means of block randomisation to receive either CoronaVac at 1·5 μg or 3·0 μg per dose, or alum only. All participants, investigators, and laboratory staff were masked to group allocation. The primary safety endpoint was adverse reactions within 28 days after each injection in all participants who received at least one dose. The primary immunogenicity endpoint assessed in the per-protocol population was seroconversion rate of neutralising antibody to live SARS-CoV-2 at 28 days after the second injection. This study is ongoing and is registered with ClinicalTrials.gov, NCT04551547., Findings: Between Oct 31, 2020, and Dec 2, 2020, 72 participants were enrolled in phase 1, and between Dec 12, 2020, and Dec 30, 2020, 480 participants were enrolled in phase 2. 550 participants received at least one dose of vaccine or alum only (n=71 for phase 1 and n=479 for phase 2; safety population). In the combined safety profile of phase 1 and phase 2, any adverse reactions within 28 days after injection occurred in 56 (26%) of 219 participants in the 1·5 μg group, 63 (29%) of 217 in the 3·0 μg group, and 27 (24%) of 114 in the alum-only group, without significant difference (p=0·55). Most adverse reactions were mild and moderate in severity. Injection site pain was the most frequently reported event (73 [13%] of 550 participants), occurring in 36 (16%) of 219 participants in the 1·5 μg group, 35 (16%) of 217 in the 3·0 μg group, and two (2%) in the alum-only group. As of June 12, 2021, only one serious adverse event of pneumonia has been reported in the alum-only group, which was considered unrelated to vaccination. In phase 1, seroconversion of neutralising antibody after the second dose was observed in 27 of 27 participants (100·0% [95% CI 87·2-100·0]) in the 1·5 μg group and 26 of 26 participants (100·0% [86·8-100·0]) in the 3·0 μg group, with the geometric mean titres of 55·0 (95% CI 38·9-77·9) and 117·4 (87·8-157·0). In phase 2, seroconversion was seen in 180 of 186 participants (96·8% [93·1-98·8]) in the 1·5 μg group and 180 of 180 participants (100·0% [98·0-100·0]) in the 3·0 μg group, with the geometric mean titres of 86·4 (73·9-101·0) and 142·2 (124·7-162·1). There were no detectable antibody responses in the alum-only groups., Interpretation: CoronaVac was well tolerated and safe and induced humoral responses in children and adolescents aged 3-17 years. Neutralising antibody titres induced by the 3·0 μg dose were higher than those of the 1·5 μg dose. The results support the use of 3·0 μg dose with a two-immunisation schedule for further studies in children and adolescents., Funding: The Chinese National Key Research and Development Program and the Beijing Science and Technology Program., Competing Interests: Declaration of interests QG and XL are employees of Sinovac Life Sciences. YS, WY, and LW are employees of Sinovac Biotech. All other authors declare no competing interests., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: Zika virus, a flavivirus transmitted by Aedes aegypti and Aedes albopictus mosquitoes, is associated with cases of congenital malformations and neurological complications. Absence of specific treatment makes a prophylactic Zika virus vaccine an unmet medical need. We assessed safety and immunogenicity of three doses of a purified, inactivated, Zika virus vaccine candidate in healthy flavivirus-naive and flavivirus-primed adults., Methods: This two-part, multicentre, observer-blind, randomised, placebo-controlled, phase 1 trial was done at seven medical clinics in the USA and two in Puerto Rico. Eligible participants were healthy adults aged 18-49 years. Participants were randomly assigned (1:1:1:1), using a sponsor-supplied randomisation scheme, to four groups to receive two intramuscular injections, 28 days apart, of saline placebo or TAK-426 containing 2 μg, 5 μg, or 10 μg antigen. Participants, investigators, and vaccine administrating personnel were masked to group assignment. Part 1 of the study assessed flavivirus-naive participants and part 2 assessed flavivirus-primed participants. The primary outcomes were safety, tolerability, and immunogenicity based on solicited local reactions and solicited systemic adverse events in the 7 days after each dose; unsolicited adverse events and serious adverse events in the 28 days after each dose; and geometric mean titres (GMTs) of neutralising anti-Zika virus antibodies at 28 days after the second dose. Safety assessments were done in all participants who received at least one dose of vaccine. Immunogenicity assessments were in the per-protocol set, comprising all participants who received at least one dose of vaccine and provided valid serology results at baseline and at least one post-vaccination timepoint, with no major protocol violations. The trial is ongoing and is registered at ClinicalTrials.gov (NCT03343626)., Findings: Between Nov 13, 2017, and Oct 24, 2018, 894 volunteers were screened and 271 enrolled (125 flavivirus-naive and 146 flavivirus-primed participants). All TAK-426 doses were well tolerated with no deaths, no vaccine-related serious adverse events, and similar rates of mainly mild to moderate adverse events. TAK-426 elicited dose-dependent increases in antibody GMTs in both flavivirus-naive and flavivirus-primed participants. 28 days after dose 2, plaque-reduction neutralisation test GMTs in flavivirus-naive participants were 1130 (95% CI 749-1703) in the 2 μg TAK-426 group, 1992 (1401-2833) in the 5 μg TAK-426 group, and 3690 (2677-5086) in the 10 μg TAK-426 group. In pairwise comparisons, responses after two vaccinations in the 10 μg group were significantly greater than in the 2 μg group (GMT ratio 3·27 [95% CI 1·98-5·39], p<0·0001) and the 5 μg group (GMT ratio 1·85 [1·15-2·98], p=0·012)., Interpretation: TAK-426 was well tolerated, with an acceptable safety profile, and was immunogenic in both flavivirus-naive and flavivirus-primed adults. Based on the safety and immunogenicity profiles of all TAK-426 doses assessed, the 10 μg TAK-426 dose was selected for further clinical development., Funding: Takeda Vaccines and the US Biomedical Advanced Research and Development Authority., Translation: For the Spanish translation of the abstract see Supplementary Materials section., Competing Interests: Declaration of interests H-HH, CJA, ML, and AB were employees of Takeda during the study. All other authors declare no competing interests., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the rapidly spreading pandemic COVID-19 in the world. As an effective therapeutic strategy is not introduced yet and the rapid genetic variations in the virus, there is an emerging necessity to design, evaluate and apply effective new vaccines. An acceptable vaccine must elicit both humoral and cellular immune responses, must have the least side effects and the storage and transport systems should be available and affordable for all countries. These vaccines can be classified into different types: inactivated vaccines, live-attenuated virus vaccines, subunit vaccines, virus-like particles (VLPs), nucleic acid-based vaccines (DNA and RNA) and recombinant vector-based vaccines (replicating and non-replicating viral vector). According to the latest update of the WHO report on April 2nd, 2021, at least 85 vaccine candidates were being studied in clinical trial phases and 184 candidate vaccines were being evaluated in pre-clinical stages. In addition, studies have shown that other vaccines, including the Bacillus Calmette-Guérin (BCG) vaccine and the Plant-derived vaccine, may play a role in controlling pandemic COVID-19. Herein, we reviewed the different types of COVID-19 candidate vaccines that are currently being evaluated in preclinical and clinical trial phases along with advantages, disadvantages or adverse reactions, if any., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: BBV152 is a whole-virion inactivated SARS-CoV-2 vaccine (3 μg or 6 μg) formulated with a toll-like receptor 7/8 agonist molecule (IMDG) adsorbed to alum (Algel). We previously reported findings from a double-blind, multicentre, randomised, controlled phase 1 trial on the safety and immunogenicity of three different formulations of BBV152 (3 μg with Algel-IMDG, 6 μg with Algel-IMDG, or 6 μg with Algel) and one Algel-only control (no antigen), with the first dose administered on day 0 and the second dose on day 14. The 3 μg and 6 μg with Algel-IMDG formulations were selected for this phase 2 study. Herein, we report interim findings of the phase 2 trial on the immunogenicity and safety of BBV152, with the first dose administered on day 0 and the second dose on day 28., Methods: We did a double-blind, randomised, multicentre, phase 2 clinical trial to evaluate the immunogenicity and safety of BBV152 in healthy adults and adolescents (aged 12-65 years) at nine hospitals in India. Participants with positive SARS-CoV-2 nucleic acid and serology tests were excluded. Participants were randomly assigned (1:1) to receive either 3 μg with Algel-IMDG or 6 μg with Algel-IMDG. Block randomisation was done by use of an interactive web response system. Participants, investigators, study coordinators, study-related personnel, and the sponsor were masked to treatment group allocation. Two intramuscular doses of vaccine were administered on day 0 and day 28. The primary outcome was SARS-CoV-2 wild-type neutralising antibody titres and seroconversion rates (defined as a post-vaccination titre that was at least four-fold higher than the baseline titre) at 4 weeks after the second dose (day 56), measured by use of the plaque-reduction neutralisation test (PRNT 50 ) and the microneutralisation test (MNT 50 ). The primary outcome was assessed in all participants who had received both doses of the vaccine. Cell-mediated responses were a secondary outcome and were assessed by T-helper-1 (Th1)/Th2 profiling at 2 weeks after the second dose (day 42). Safety was assessed in all participants who received at least one dose of the vaccine. In addition, we report immunogenicity results from a follow-up blood draw collected from phase 1 trial participants at 3 months after they received the second dose (day 104). This trial is registered at ClinicalTrials.gov, NCT04471519., Findings: Between Sept 5 and 12, 2020, 921 participants were screened, of whom 380 were enrolled and randomly assigned to the 3 μg with Algel-IMDG group (n=190) or 6 μg with Algel-IMDG group (n=190). Geometric mean titres (GMTs; PRNT 50 ) at day 56 were significantly higher in the 6 μg with Algel-IMDG group (197·0 [95% CI 155·6-249·4]) than the 3 μg with Algel-IMDG group (100·9 [74·1-137·4]; p=0·0041). Seroconversion based on PRNT 50 at day 56 was reported in 171 (92·9% [95% CI 88·2-96·2] of 184 participants in the 3 μg with Algel-IMDG group and 174 (98·3% [95·1-99·6]) of 177 participants in the 6 μg with Algel-IMDG group. GMTs (MNT 50 ) at day 56 were 92·5 (95% CI 77·7-110·2) in the 3 μg with Algel-IMDG group and 160·1 (135·8-188·8) in the 6 μg with Algel-IMDG group. Seroconversion based on MNT 50 at day 56 was reported in 162 (88·0% [95% CI 82·4-92·3]) of 184 participants in the 3 μg with Algel-IMDG group and 171 (96·6% [92·8-98·8]) of 177 participants in the 6 μg with Algel-IMDG group. The 3 μg with Algel-IMDG and 6 μg with Algel-IMDG formulations elicited T-cell responses that were biased to a Th1 phenotype at day 42. No significant difference in the proportion of participants who had a solicited local or systemic adverse reaction in the 3 μg with Algel-IMDG group (38 [20·0%; 95% CI 14·7-26·5] of 190) and the 6 μg with Algel-IMDG group (40 [21·1%; 15·5-27·5] of 190) was observed on days 0-7 and days 28-35; no serious adverse events were reported in the study. From the phase 1 trial, 3-month post-second-dose GMTs (MNT 50 ) were 39·9 (95% CI 32·0-49·9) in the 3μg with Algel-IMDG group, 69·5 (53·7-89·9) in the 6 μg with Algel-IMDG group, 53·3 (40·1-71·0) in the 6 μg with Algel group, and 20·7 (14·5-29·5) in the Algel alone group., Interpretation: In the phase 1 trial, BBV152 induced high neutralising antibody responses that remained elevated in all participants at 3 months after the second vaccination. In the phase 2 trial, BBV152 showed better reactogenicity and safety outcomes, and enhanced humoral and cell-mediated immune responses compared with the phase 1 trial. The 6 μg with Algel-IMDG formulation has been selected for the phase 3 efficacy trial., Funding: Bharat Biotech International., Translation: For the Hindi translation of the abstract see Supplementary Materials section., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: A vaccine against COVID-19 is urgently needed for older adults, in whom morbidity and mortality due to the disease are increased. We aimed to assess the safety, tolerability, and immunogenicity of a candidate COVID-19 vaccine, CoronaVac, containing inactivated SARS-CoV-2, in adults aged 60 years and older., Methods: We did a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial of CoronaVac in healthy adults aged 60 years and older in Renqiu (Hebei, China). Vaccine or placebo was given by intramuscular injection in two doses (days 0 and 28). Phase 1 comprised a dose-escalation study, in which participants were allocated to two blocks: block 1 (3 μg inactivated virus in 0·5 mL of aluminium hydroxide solution per injection) and block 2 (6 μg per injection). Within each block, participants were randomly assigned (2:1) using block randomisation to receive CoronaVac or placebo (aluminium hydroxide solution only). In phase 2, participants were randomly assigned (2:2:2:1) using block randomisation to receive either CoronaVac at 1·5 μg, 3 μg, or 6 μg per dose, or placebo. All participants, investigators, and laboratory staff were masked to treatment allocation. The primary safety endpoint was adverse reactions within 28 days after each injection in all participants who received at least one dose. The primary immunogenicity endpoint was seroconversion rate at 28 days after the second injection (which was assessed in all participants who had received the two doses of vaccine according to their random assignment, had antibody results available, and did not violate the trial protocol). Seroconversion was defined as a change from seronegative at baseline to seropositive for neutralising antibodies to live SARS-CoV-2 (positive cutoff titre 1/8), or a four-fold titre increase if the participant was seropositive at baseline. This study is ongoing and is registered with ClinicalTrials.gov (NCT04383574)., Findings: Between May 22 and June 1, 2020, 72 participants (24 in each intervention group and 24 in the placebo group; mean age 65·8 years [SD 4·8]) were enrolled in phase 1, and between June 12 and June 15, 2020, 350 participants were enrolled in phase 2 (100 in each intervention group and 50 in the placebo group; mean age 66·6 years [SD 4·7] in 349 participants). In the safety populations from both phases, any adverse reaction within 28 days after injection occurred in 20 (20%) of 100 participants in the 1·5 μg group, 25 (20%) of 125 in the 3 μg group, 27 (22%) of 123 in the 6 μg group, and 15 (21%) of 73 in the placebo group. All adverse reactions were mild or moderate in severity and injection site pain (39 [9%] of 421 participants) was the most frequently reported event. As of Aug 28, 2020, eight serious adverse events, considered unrelated to vaccination, have been reported by seven (2%) participants. In phase 1, seroconversion after the second dose was observed in 24 of 24 participants (100·0% [95% CI 85·8-100·0]) in the 3 μg group and 22 of 23 (95·7% [78·1-99·9]) in the 6 μg group. In phase 2, seroconversion was seen in 88 of 97 participants in the 1·5 μg group (90·7% [83·1-95·7]), 96 of 98 in the 3 μg group (98·0% [92·8-99·8]), and 97 of 98 (99·0% [94·5-100·0]) in the 6 μg group. There were no detectable antibody responses in the placebo groups., Interpretation: CoronaVac is safe and well tolerated in older adults. Neutralising antibody titres induced by the 3 μg dose were similar to those of the 6 μg dose, and higher than those of the 1·5 μg dose, supporting the use of the 3 μg dose CoronaVac in phase 3 trials to assess protection against COVID-19., Funding: Chinese National Key Research and Development Program and Beijing Science and Technology Program., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: To mitigate the effects of COVID-19, a vaccine is urgently needed. BBV152 is a whole-virion inactivated SARS-CoV-2 vaccine formulated with a toll-like receptor 7/8 agonist molecule adsorbed to alum (Algel-IMDG) or alum (Algel)., Methods: We did a double-blind, multicentre, randomised, controlled phase 1 trial to assess the safety and immunogenicity of BBV152 at 11 hospitals across India. Healthy adults aged 18-55 years who were deemed healthy by the investigator were eligible. Individuals with positive SARS-CoV-2 nucleic acid and/or serology tests were excluded. Participants were randomly assigned to receive either one of three vaccine formulations (3 μg with Algel-IMDG, 6 μg with Algel-IMDG, or 6 μg with Algel) or an Algel only control vaccine group. Block randomisation was done with a web response platform. Participants and investigators were masked to treatment group allocation. Two intramuscular doses of vaccines were administered on day 0 (the day of randomisation) and day 14. Primary outcomes were solicited local and systemic reactogenicity events at 2 h and 7 days after vaccination and throughout the full study duration, including serious adverse events. Secondary outcome was seroconversion (at least four-fold increase from baseline) based on wild-type virus neutralisation. Cell-mediated responses were evaluated by intracellular staining and ELISpot. The trial is registered at ClinicalTrials.gov (NCT04471519)., Findings: Between July 13 and 30, 2020, 827 participants were screened, of whom 375 were enrolled. Among the enrolled participants, 100 each were randomly assigned to the three vaccine groups, and 75 were randomly assigned to the control group (Algel only). After both doses, solicited local and systemic adverse reactions were reported by 17 (17%; 95% CI 10·5-26·1) participants in the 3 μg with Algel-IMDG group, 21 (21%; 13·8-30·5) in the 6 μg with Algel-IMDG group, 14 (14%; 8·1-22·7) in the 6 μg with Algel group, and ten (10%; 6·9-23·6) in the Algel-only group. The most common solicited adverse events were injection site pain (17 [5%] of 375 participants), headache (13 [3%]), fatigue (11 [3%]), fever (nine [2%]), and nausea or vomiting (seven [2%]). All solicited adverse events were mild (43 [69%] of 62) or moderate (19 [31%]) and were more frequent after the first dose. One serious adverse event of viral pneumonitis was reported in the 6 μg with Algel group, unrelated to the vaccine. Seroconversion rates (%) were 87·9, 91·9, and 82·8 in the 3 μg with Algel-IMDG, 6 μg with Algel-IMDG, and 6 μg with Algel groups, respectively. CD4 + and CD8 + T-cell responses were detected in a subset of 16 participants from both Algel-IMDG groups., Interpretation: BBV152 led to tolerable safety outcomes and enhanced immune responses. Both Algel-IMDG formulations were selected for phase 2 immunogenicity trials. Further efficacy trials are warranted., Funding: Bharat Biotech International., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: With the unprecedented morbidity and mortality associated with the COVID-19 pandemic, a vaccine against COVID-19 is urgently needed. We investigated CoronaVac (Sinovac Life Sciences, Beijing, China), an inactivated vaccine candidate against COVID-19, containing inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), for its safety, tolerability and immunogenicity., Methods: In this randomised, double-blind, placebo-controlled, phase 1/2 clinical trial, healthy adults aged 18-59 years were recruited from the community in Suining County of Jiangsu province, China. Adults with SARS-CoV-2 exposure or infection history, with axillary temperature above 37·0°C, or an allergic reaction to any vaccine component were excluded. The experimental vaccine for the phase 1 trial was manufactured using a cell factory process (CellSTACK Cell Culture Chamber 10, Corning, Wujiang, China), whereas those for the phase 2 trial were produced through a bioreactor process (ReadyToProcess WAVE 25, GE, Umea, Sweden). The phase 1 trial was done in a dose-escalating manner. At screening, participants were initially separated (1:1), with no specific randomisation, into two vaccination schedule cohorts, the days 0 and 14 vaccination cohort and the days 0 and 28 vaccination cohort, and within each cohort the first 36 participants were assigned to block 1 (low dose CoronaVac [3 μg per 0·5 mL of aluminium hydroxide diluent per dose) then another 36 were assigned to block 2 (high-dose Coronavc [6 μg per 0·5 mL of aluminium hydroxide diluent per dse]). Within each block, participants were randomly assigned (2:1), using block randomisation with a block size of six, to either two doses of CoronaVac or two doses of placebo. In the phase 2 trial, at screening, participants were initially separated (1:1), with no specific randomisation, into the days 0 and 14 vaccination cohort and the days 0 and 28 vaccination cohort, and participants were randomly assigned (2:2:1), using block randomisation with a block size of five, to receive two doses of either low-dose CoronaVac, high-dose CoronaVac, or placebo. Participants, investigators, and laboratory staff were masked to treatment allocation. The primary safety endpoint was adverse reactions within 28 days after injection in all participants who were given at least one dose of study drug (safety population). The primary immunogenic outcome was seroconversion rates of neutralising antibodies to live SARS-CoV-2 at day 14 after the last dose in the days 0 and 14 cohort, and at day 28 after the last dose in the days 0 and 28 cohort in participants who completed their allocated two-dose vaccination schedule (per-protocol population). This trial is registered with ClinicalTrials.gov, NCT04352608, and is closed to accrual., Findings: Between April 16 and April 25, 2020, 144 participants were enrolled in the phase 1 trial, and between May 3 and May 5, 2020, 600 participants were enrolled in the phase 2 trial. 743 participants received at least one dose of investigational product (n=143 for phase 1 and n=600 for phase 2; safety population). In the phase 1 trial, the incidence of adverse reactions for the days 0 and 14 cohort was seven (29%) of 24 participants in the 3 ug group, nine (38%) of 24 in the 6 μg group, and two (8%) of 24 in the placebo group, and for the days 0 and 28 cohort was three (13%) of 24 in the 3 μg group, four (17%) of 24 in the 6 μg group, and three (13%) of 23 in the placebo group. The seroconversion of neutralising antibodies on day 14 after the days 0 and 14 vaccination schedule was seen in 11 (46%) of 24 participants in the 3 μg group, 12 (50%) of 24 in the 6 μg group, and none (0%) of 24 in the placebo group; whereas at day 28 after the days 0 and 28 vaccination schedule, seroconversion was seen in 20 (83%) of 24 in the 3 μg group, 19 (79%) of 24 in the 6 μg group, and one (4%) of 24 in the placebo group. In the phase 2 trial, the incidence of adverse reactions for the days 0 and 14 cohort was 40 (33%) of 120 participants in the 3 μg group, 42 (35%) of 120 in the 6 μg group, and 13 (22%) of 60 in the placebo group, and for the days 0 and 28 cohort was 23 (19%) of 120 in the 3 μg group, 23 (19%) of 120 in the 6 μg group, and 11 (18%) of 60 for the placebo group. Seroconversion of neutralising antibodies was seen for 109 (92%) of 118 participants in the 3 μg group, 117 (98%) of 119 in the 6 μg group, and two (3%) of 60 in the placebo group at day 14 after the days 0 and 14 schedule; whereas at day 28 after the days 0 and 28 schedule, seroconversion was seen in 114 (97%) of 117 in the 3 μg group, 118 (100%) of 118 in the 6 μg group, and none (0%) of 59 in the placebo group., Interpretation: Taking safety, immunogenicity, and production capacity into account, the 3 μg dose of CoronaVac is the suggested dose for efficacy assessment in future phase 3 trials., Funding: Chinese National Key Research and Development Program and Beijing Science and Technology Program., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: The ongoing COVID-19 pandemic warrants accelerated efforts to test vaccine candidates. We aimed to assess the safety and immunogenicity of an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine candidate, BBIBP-CorV, in humans., Methods: We did a randomised, double-blind, placebo-controlled, phase 1/2 trial at Shangqiu City Liangyuan District Center for Disease Control and Prevention in Henan Province, China. In phase 1, healthy people aged 18-80 years, who were negative for serum-specific IgM/IgG antibodies against SARS-CoV-2 at the time of screening, were separated into two age groups (18-59 years and ≥60 years) and randomly assigned to receive vaccine or placebo in a two-dose schedule of 2 μg, 4 μg, or 8 μg on days 0 and 28. In phase 2, healthy adults (aged 18-59 years) were randomly assigned (1:1:1:1) to receive vaccine or placebo on a single-dose schedule of 8 μg on day 0 or on a two-dose schedule of 4 μg on days 0 and 14, 0 and 21, or 0 and 28. Participants within each cohort were randomly assigned by stratified block randomisation (block size eight) and allocated (3:1) to receive vaccine or placebo. Group allocation was concealed from participants, investigators, and outcome assessors. The primary outcomes were safety and tolerability. The secondary outcome was immunogenicity, assessed as the neutralising antibody responses against infectious SARS-CoV-2. This study is registered with www.chictr.org.cn, ChiCTR2000032459., Findings: In phase 1, 192 participants were enrolled (mean age 53·7 years [SD 15·6]) and were randomly assigned to receive vaccine (2 μg [n=24], 4 μg [n=24], or 8 μg [n=24] for both age groups [18-59 years and ≥60 years]) or placebo (n=24). At least one adverse reaction was reported within the first 7 days of inoculation in 42 (29%) of 144 vaccine recipients. The most common systematic adverse reaction was fever (18-59 years, one [4%] in the 2 μg group, one [4%] in the 4 μg group, and two [8%] in the 8 μg group; ≥60 years, one [4%] in the 8 μg group). All adverse reactions were mild or moderate in severity. No serious adverse event was reported within 28 days post vaccination. Neutralising antibody geometric mean titres were higher at day 42 in the group aged 18-59 years (87·7 [95% CI 64·9-118·6], 2 μg group; 211·2 [158·9-280·6], 4 μg group; and 228·7 [186·1-281·1], 8 μg group) and the group aged 60 years and older (80·7 [65·4-99·6], 2 μg group; 131·5 [108·2-159·7], 4 μg group; and 170·87 [133·0-219·5], 8 μg group) compared with the placebo group (2·0 [2·0-2·0]). In phase 2, 448 participants were enrolled (mean age 41·7 years [SD 9·9]) and were randomly assigned to receive the vaccine (8 μg on day 0 [n=84] or 4 μg on days 0 and 14 [n=84], days 0 and 21 [n=84], or days 0 and 28 [n=84]) or placebo on the same schedules (n=112). At least one adverse reaction within the first 7 days was reported in 76 (23%) of 336 vaccine recipients (33 [39%], 8 μg day 0; 18 [21%], 4 μg days 0 and 14; 15 [18%], 4 μg days 0 and 21; and ten [12%], 4 μg days 0 and 28). One placebo recipient in the 4 μg days 0 and 21 group reported grade 3 fever, but was self-limited and recovered. All other adverse reactions were mild or moderate in severity. The most common systematic adverse reaction was fever (one [1%], 8 μg day 0; one [1%], 4 μg days 0 and 14; three [4%], 4 μg days 0 and 21; two [2%], 4 μg days 0 and 28). The vaccine-elicited neutralising antibody titres on day 28 were significantly greater in the 4 μg days 0 and 14 (169·5, 95% CI 132·2-217·1), days 0 and 21 (282·7, 221·2-361·4), and days 0 and 28 (218·0, 181·8-261·3) schedules than the 8 μg day 0 schedule (14·7, 11·6-18·8; all p<0·001)., Interpretation: The inactivated SARS-CoV-2 vaccine, BBIBP-CorV, is safe and well tolerated at all tested doses in two age groups. Humoral responses against SARS-CoV-2 were induced in all vaccine recipients on day 42. Two-dose immunisation with 4 μg vaccine on days 0 and 21 or days 0 and 28 achieved higher neutralising antibody titres than the single 8 μg dose or 4 μg dose on days 0 and 14., Funding: National Program on Key Research Project of China, National Mega projects of China for Major Infectious Diseases, National Mega Projects of China for New Drug Creation, and Beijing Science and Technology Plan., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The morbidity and mortality of coxsackievirus A10 (CVA10)-associated hand, foot, and mouth disease (HFMD) have been increasing in recent years, while few studies on the vaccine and animal model of CVA10 have been reported. Here, we first established a CVA10-infected gerbil model and employed it to evaluate the immunoprotective effect of an inactivated CVA10 vaccine. The results showed that gerbils up to the age of 14 days were fully susceptible to CVA10, and all died within five days post-infection by intraperitoneal inoculation. Lethargy, wasting, hind-limb paralysis, and even death could be observed in the CVA10-infected gerbils. Pathological examination suggested that CVA10 has a strong tropism toward muscle tissue, and muscle bundle fracture and muscular fibers necrosis were observed in the limb muscles. Additionally, active immunization results showed that gerbils immunized with the inactivated CVA10 vaccine were 100 % protected from lethal CVA10 challenge. The antisera from vaccinated gerbils also showed high neutralizing titers against CVA10. Based on these results, the CVA10-infected gerbil model was a suitable tool for analyzing the pathogenesis of CVA10 and assessing the protective efficacy of CVA10 candidate vaccines., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The development of an effective vaccine against Zika virus remains a public health priority. A Zika purified inactivated virus (ZPIV) vaccine candidate has been shown to protect animals against Zika virus challenge and to be well tolerated and immunogenic in humans up to 8 weeks of follow-up. We aimed to assess the safety and immunogenicity of ZPIV in humans up to 52 weeks of follow-up when given via standard or accelerated vaccination schedules., Methods: We did a single-centre, double-blind, randomised controlled, phase 1 trial in healthy adults aged 18-50 years with no known history of flavivirus vaccination or infection at Beth Israel Deaconess Medical Center in Boston, MA, USA. Participants were sequentially enrolled into one of three groups: ZPIV given at weeks 0 and 4 (standard regimen), weeks 0 and 2 (accelerated regimen), or week 0 alone (single-dose regimen). Within each group, participants were randomly assigned using a computer-generated randomisation schedule to receive an intramuscular injection of 5 μg ZPIV or saline placebo, in a ratio of 5:1. The sponsor, clinical staff, investigators, participants, and laboratory personnel were masked to treatment assignment. The primary endpoint was safety up to day 364 after final dose administration, and secondary endpoints were proportion of participants with positive humoral immune responses (50% microneutralisation titre [MN 50 ] ≥100) and geometric mean MN 50 at observed peak response (ie, the highest neutralising antibody level observed for an individual participant across all timepoints) and week 28. All participants who received at least one dose of ZPIV or placebo were included in the safety population; the analysis of immunogenicity at observed peak included all participants who received at least one dose of ZPIV or placebo and had any adverse events or immunogenicity data after dosing. The week 28 immunogenicity analysis population consisted of all participants who received ZPIV or placebo and had immunogenicity data available at week 28. This trial is registered with ClinicalTrials.gov, NCT02937233., Findings: Between Dec 8, 2016, and May 17, 2017, 12 participants were enrolled into each group and then randomly assigned to vaccine (n=10) or placebo (n=2). There were no serious or grade 3 treatment-related adverse events. The most common reactions among the 30 participants who received the vaccine were injection-site pain (24 [80%]), fatigue (16 [53%]), and headache (14 [46%]). A positive response at observed peak titre was detected in all participants who received ZPIV via the standard regimen, in eight (80%) of ten participants who received ZPIV via the accelerated regimen, and in none of the ten participants who received ZPIV via the single-dose regimen. The geometric mean of all individual participants' observed peak values was 1153·9 (95% CI 455·2-2925·2) in the standard regimen group, 517·7 (142·9-1875·6) in the accelerated regimen group, and 6·3 (3·7-10·8) in the single-dose regimen group. At week 28, a positive response was observed in one (13%) of eight participants who received ZPIV via the standard regimen and in no participant who received ZPIV via the accelerated (n=7) or single-dose (n=10) regimens. The geomteric mean titre (GMT) at this timepoint was 13·9 (95% CI 3·5-55·1) in the standard regimen group and 6·9 (4·0-11·9) in the accelerated regimen group; antibody titres were undetectable at 28 weeks in participants who received ZPIV via the single-dose regimen. For all vaccine schedules, GMTs peaked 2 weeks after the final vaccination and declined to less than 100 by study week 16. There was no difference in observed peak GMTs between the standard 4-week and the accelerated 2-week boosting regimens (p=0·4494)., Interpretation: ZPIV was safe and well tolerated in humans up to 52 weeks of follow-up. ZPIV immunogenicity required two doses and was not durable. Additional studies of ZPIV to optimise dosing schedules are ongoing., Funding: The Henry M Jackson Foundation for the Advancement of Military Medicine., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus that causes acute diarrhea, vomiting, dehydration and mortality in neonatal piglets, resulting in significant economic losses to the pig industry. However, there is currently little information on vaccine studies and commercially available vaccines for PDCoV. Hence, herein, a PDCoV strain, CH/XJYN/2016, was successfully isolated and serially propagated in vitro, and its biological characteristics were determined. Compared to that of previously reported and recently isolated PDCoV strains from China and the United States, the S gene of the CH/XJYN/2016 strain contains novel mutations. Infection studies revealed that CH/XJYN/2016 is pathogenic to suckling piglets and conventional weaned pigs. In addition, the median pig diarrhea dose (PDD 50 ) of PDCoV in conventional weaned pigs was determined (2.0 log 10 PDD 50 /3 mL). Furthermore, an inactivated cell-adapted CH/XJYN/2016-based vaccine candidate was developed with different adjuvants. Compared with nonvaccinated pigs, conventional weaned pigs given the inactivated vaccine developed a potent humoral immune response and showed no clinical signs or viral shedding after challenge, indicating a potent protective effect of the vaccine against PDCoV infection. Therefore, the PDCoV vaccine developed in this study is a promising vaccine candidate that can be used for the control of PDCoV infection in pigs., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Quadrivalent influenza vaccines are particularly valuable during seasons in which a mismatch occurs between the predicted influenza B lineage for the trivalent influenza vaccine and the circulating strain. This study evaluated the immunogenicity and safety of a quadrivalent inactivated influenza vaccine AdimFlu-S manufactured in Taiwan for the 2016-2017 influenza season in healthy children., Methods: A total of 174 healthy children aged 3 to 17 years old were separated into 3 groups (Group A: 3-8 years old, vaccine naïve; Group B: 3-8 years old, vaccine non-naïve; Group C: 9-17 years old, any vaccine status). Sera was collected pre and post vaccination for each participant. A hemagglutination inhibition (HAI) assay was utilized to calculate geometric mean titer (GMT), seroprotection rate, and seroconversion rate., Results: All enrolled participants completed the study. For the four vaccine strains four weeks after the last vaccination, geometric mean titer ratios (GMTRs) were between 2.9 and 20.9, seroconversion rates were between 42.9% and 90.9%, and seroprotection rates were all above 96.4%. This achieved all immunogenicity endpoints and fulfilled the criteria of the European Medical Agency's Committee for Medicinal Products for Human Use (CHMP). No serious adverse events (AEs) were reported during the follow-up period of 6 months., Conclusion: This quadrivalent influenza vaccine is demonstrated to be well tolerated and displays robust immunogenicity for each influenza strain. This could potentially improve protection against the antigenically distinct B/Yamagata and B/Victoria lineages., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Dengue fever, caused by dengue viruses (DENV 1-4) is a leading cause of illness and death in the tropics and subtropics. Therefore, an effective vaccine is urgently needed. Currently, the only available licensed dengue vaccine is a chimeric live attenuated vaccine that shows varying efficacy depending on serotype, age and baseline DENV serostatus. Accordingly, a dengue vaccine that is effective in seronegative adults, children of all ages and in immunocompromised individuals is still needed. We are currently researching the use of psoralen to develop an inactivated tetravalent dengue vaccine. Unlike traditional formalin inactivation, psoralen inactivates pathogens at the nucleic acid level, potentially preserving envelope protein epitopes important for protective anti-dengue immune responses. We prepared highly purified monovalent vaccine lots of formalin- and psoralen-inactivated DENV 1-4, using Capto DeVirS and Capto Core 700 resin based column chromatography. Tetravalent psoralen-inactivated vaccines (PsIV) and formalin-inactivated vaccines (FIV) were prepared by combining the four monovalent vaccines. Mice were immunized with either a low or high dose of PsIV or FIV to evaluate the immunogenicity of monovalent as well as tetravalent formulations of each inactivation method. In general, the monovalent and tetravalent PsIVs elicited equivalent or higher titers of neutralizing antibodies to DENV than the FIV dengue vaccines and this response was dose dependent. The immunogenicity of tetravalent dengue PsIVs and FIVs were also evaluated in nonhuman primates (NHPs). Consistent with what was observed in mice, significantly higher neutralizing antibody titers for each dengue serotype were observed in the NHPs vaccinated with the tetravalent dengue PsIV compared to those vaccinated with the tetravalent dengue FIV, indicative of the importance of envelope protein epitope preservation during psoralen inactivation of DENV., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Dr. Kevin Porter holds a patent on “Psoralen-inactivated viral vaccine and method of preparation”. Patent No.: US 9005633B2]., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Licensed inactivated influenza vaccines (IIV) are recommended for persons aged ≥65 years, including trivalent high-dose IIV (HD-IIV3) and adjuvanted IIV (aIIV3); both are manufactured in eggs. Quadrivalent recombinant vaccine (RIV4) is produced without eggs. We conducted an exploratory study to compare immunogenicity of HD-IIV3, aIIV3 and RIV4 against cell-grown vaccine and circulating A(H3N2) viruses in 2017-18., Methods: Eighty-nine adults aged 65-74 years participating in a 2-year, open-label immunogenicity trial (ClinicalTrails.gov: NCT02872311) were randomized 1:1:1 to receive HD-IIV3, aIIV3, or RIV4 after receipt of standard dose IIV3 in 2016-17. Serum was obtained at baseline and day 28 post vaccination. Microneutralization titers were determined using four cell-propagated A(H3N2) viruses: 2017-18 vaccine strain (clade 3C.2a), circulating viruses from clades 3C.2a1 and 3C.2a2, and 'antigenically advanced' clade 3C.3a (2019-20 vaccine strain). Active surveillance was conducted to identify influenza illnesses., Results: Post vaccination geometric mean titer (GMT) against the vaccine strain was <1:60 in each group and <15% seroconverted. RIV4 generated a greater fold-rise (2.0, 95% CI 1.7-2.5) compared to HD-IIV3 (1.6, 95% CI 1.3-1.8). RIV4 generated higher post vaccination titers against 3C.2a1 and 3C.2a2 viruses, and the mean fold-rise after RIV4 was twice as high (3.3 and 3.5, respectively) relative to HD-IIV3 (1.4 and 1.6) and aIIV3 (1.7 and 1.6). Against the antigenically advanced 3C.3a virus, RIV4 generated a greater mean fold-rise (2.9, 95% CI 2.0-4.3) vs HD-IIV3 (1.3, 95% CI 1.1-1.6) and aIIV3 (1.7, 95% CI 1.3-2.1). Postvaccination titers against 3C.2a2 were ≥1:40 in 5 of 7 participants with PCR-confirmed A(H3N2) infection during the ensuing influenza season., Conclusion: High-dose, adjuvanted, and recombinant vaccines generated suboptimal neutralizing antibody responses to the cell-grown vaccine strain, but RIV4 generated a greater cross-protective response against circulating and antigenically advanced viruses. Recombinant technology may contribute to more broadly protective influenza vaccines, and comparative effectiveness studies are needed., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Huong McLean receives research support from Seqirus. The other authors declare no competing interests.]., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: In China, three inactivated Enterovirus 71 (EV71) vaccines have been approved. Although the vaccines in an immunization series should be from a single manufacture, children sometimes have to receive EV71 vaccines from more than one manufacturers. The aim of this study was to evaluate the interchangeability and safety of vaccination with EV71 vaccines from two manufacturers among Chinese children., Methods: We conducted an open label and randomized controlled study among children aged 6-35 months from November 2018 to January 2019. The participants were randomly assigned (1:1:1:1) to receive EV71 vaccines in one of the four different schedules (two using a single vaccine for all doses from one manufacture, and two mixed schedules using vaccines from two manufactures). Blood samples were collected pre-vaccination (Day 0) and one month after the second dose (Day 60) for neutralizing antibody assay. Immunogenicity was assessed in the per-protocol cohort and safety was assessed in the total vaccinated cohort., Results: A total of 300 children were enrolled and randomized, of whom 89.0% (267/300) were included in the per-protocol cohort for immunogenicity analysis. The seroconversion rates of the EV71 neutralizing antibody in four groups ranged from 98.4% to 100.0%, and were not significantly different among the groups. Compared with other groups, geometric mean titer was higher in group D, in which the participants received Institute of Medical Biology Chinese Academy of Medical Sciences (CAMS) vaccine in the first dose and the Sinovac vaccine in the second dose. Safety profiles were similar among the four groups and no serious adverse events related to the vaccination were reported., Conclusions: Interchangeability of EV71 vaccines from two manufactures to complete an immunization series showed good immunogenicity and safety. The antibody response levels may vary by vaccination sequences of EV71 vaccines from the two manufacturers., Trial Registration: ClinicalTrials.govNCT03873740., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: WQ Yang, XH Tian, J LI, NN Jia and G Zeng are employed by the Sinovac Biotech Co., LTD. All other authors report no potential conflicts., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Seasonal influenza vaccines aim to induce strain-specific neutralizing antibodies. Non-neutralizing antibodies may be more broadly cross-reactive and still protect through mechanisms including antibody-dependent cell-mediated cytotoxicity (ADCC). Influenza vaccines may stimulate ADCC antibodies in adults, but whether they do so in children is unknown. Here we examined how vaccination affects cross-reactive ADCC antibody responses in children after receipt of inactivated trivalent vaccine (IIV3) or quadrivalent live-attenuated vaccine (LAIV4)., Methods: Children aged 5-17 were recruited in fall 2014 to provide pre- and post-vaccination serum samples. Children aged 5-9 received LAIV4 based on then-current recommendation, and older children were randomly assigned to IIV3 or LAIV4. We used microtiter-plate-based flow cytometry with an NK cell line to examine ADCC antibody responses to the 2014-15 H3N2 vaccine component (A/Texas/50/2012 [TX12]) and a drifted strain, A/Switzerland/9715293/2013 (SW13). Responses were stratified by two-season (2013-14 and 2014-15) vaccine sequence., Results: Eighty-five children received LAIV4 and 45 received IIV3. Prevaccination ADCC activity was highest in children who had received any vaccine in the prior season. Increase in ADCC antibody responses against the vaccine strain TX12 following vaccination was greatest for participants who received IIV3 in 2014-15 and LAIV4 in the prior season (geometric mean fold rise [MFR] = 1.6, 95% CI. 1.23-2.11). This group also had a detectable ADCC response to the drifted SW13 strain. There was a modest ADCC response against SW13 in LAIV4 recipients who were unvaccinated in the previous season (MFR = 1.18, 95% CI 1.10-1.25). There were no significant changes in 2014-15 ADCC response to vaccination among children who had received IIV3 in 2013-14., Conclusions: Vaccinating children with IIV3 after prior receipt of LAIV4 generated a modest increase in ADCC antibodies, including some cross-reactivity with an emerging drift variant. Other vaccine-induced ADCC responses were minimal and not affected by vaccine type or sequence., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Enterovirus type 71 (EV71) and coxsackievirus A 16 (CA16) are recognized as the major pathogens responsible for human hand-foot-mouth disease. To develop a bivalent EV71-CA16 vaccine, rhesus macaques immunized with two doses of this vaccine via the intradermal route were challenged with EV71 or CA16, and their clinical symptoms, viral shedding, neutralizing antibodies, IFN-γ-specific ELISpots, and tissue viral load were examined longitudinally. Specific immunity against EV71 and CA16 was observed in the macaques, which exhibited controlled proliferation of the EV71 and CA16 viruses and upregulated expression of immune-related genes compared with the controls. Furthermore, broad protection against EV71 and CA16 challenge without immunopathological effects was observed in all the immunized macaques. These studies suggest that the bivalent EV71-CA16 inactivated vaccine was effective against wild-type EV71 or CA16 viral challenge in rhesus macaques., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Children and adolescents are susceptible to influenza. Vaccination is the most important strategy for preventing influenza, yet there are few studies on the immunogenicity and safety of quadrivalent inactivated influenza vaccine (QIV) containing two A strains (H1N1 and H3N2) and two B lineages (Victoria and Yamagata). Therefore, to further clarify the immunogenicity and safety of QIV in children and adolescents, a meta-analysis was performed to provide a reference for the development of influenza prevention strategies., Methods: PubMed, EMBASE and Cochrane Library were searched for articles published as of February 12, 2019. Random clinical trials comparing the immunogenicity and safety of QIV and TIV among children and adolescents were selected. The main outcomes were comparisons of immunogenicity (seroprotection rate [SPR] and seroconversion rate [SCR] and adverse events using risk ratios (RRs). The meta-analysis was performed using random-effects models., Results: Among the 6 months up to 3 years group, QIV showed a higher SPR for B lineages than for TIV-B/Yamagata, with pooled RRs of 3.07 (95% CI: 2.58-3.66) and 1.06 (95% CI: 1.01-1.11), respectively. For the 3 years through 18 years, QIV had a higher SCR and SPR for the Yamagata lineage than for TIV-B/Victoria, with pooled RRs of 2.30 (95% CI: 1.83-2.88) and 1.16 (95% CI: 1.03-1.30), respectively. Compared to TIV-B/Yamagata, a higher SCR and SPR for the Victoria lineage was found for QIV, with RRs of 3.09 (95% CI: 1.99-4.78) and 1.72 (95% CI: 1.22-2.41), respectively. Regarding adverse events, only pain was more frequently reported for QIV than TIV ; the RR was 1.09 (95% CI: 1.02-1.17)., Conclusions: The immunogenicity of QIV for common ingredients was similar to that of TIV, but the former exhibited significantly higher immunogenicity for the unique lineage. QIV also had the same reliable safety as TIV., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Enterotoxigenic Escherichia coli causes diarrhoea, leading to substantial mortality and morbidity in children, but no specific vaccine exists. This trial tested an oral, inactivated, enterotoxigenic E coli vaccine (ETVAX), which has been previously shown to be safe and highly immuongenic in Swedish and Bangladeshi adults. We tested the safety and immunogenicity of ETVAX, consisting of four E coli strains overexpressing the most prevalent colonisation factors (CFA/I, CS3, CS5, and CS6) and a toxoid (LCTBA) administered with or without a double-mutant heat-labile enterotoxin (dmLT) as an adjuvant, in Bangladeshi children., Methods: We did a randomised, double-blind, placebo-controlled, dose-escalation, age-descending, phase 1/2 trial in Dhaka, Bangladesh. Healthy children in one of three age groups (24-59 months, 12-23 months, and 6-11 months) were eligible. Children were randomly assigned with block randomisation to receive either ETVAX, with or without dmLT, or placebo. ETVAX (half [5·5 × 10 10 cells], quarter [2·5 × 10 10 cells], or eighth [1·25 × 10 10 cells] adult dose), with or without dmLT adjuvant (2·5 μg, 5·0 μg, or 10·0 μg), or placebo were administered orally in two doses 2 weeks apart. Investigators and participants were masked to treatment allocation. The primary endpoint was safety and tolerability, assessed in all children who received at least one dose of vaccine. Antibody responses to vaccine antigens, defined as at least a two-times increase in antibody levels between baseline and post-immunisation, were assessed as secondary endpoints. This trial is registered with ClinicalTrials.gov, NCT02531802., Findings: Between Dec 7, 2015, and Jan 10, 2017, we screened 1500 children across the three age groups, of whom 430 were enrolled and randomly assigned to the different treatment groups (130 aged 24-59 months, 100 aged 12-23 months, and 200 aged 6-11 months). All participants received at least one dose of vaccine. No solicited adverse events occurred that were greater than moderate in severity, and most were mild. The most common solicited event was vomiting (ten [8%] of 130 patients aged 24-59 months, 13 [13%] of 100 aged 12-23 months, and 29 [15%] of 200 aged 6-11 months; mostly of mild severity), which appeared related to dose and age. The addition of dmLT did not modify the safety profile. Three serious adverse events occurred but they were not considered related to the study drug. Mucosal IgA antibody responses in lymphocyte secretions were detected against all primary vaccine antigens (CFA/I, CS3, CS5, CS6, and the LCTBA toxoid) in most participants in the two older age groups, whereas such responses to four of the five antigens were less frequent and of lower magnitude in infants aged 6-11 months than in older children. Faecal secretory IgA immune responses were recorded against all vaccine antigens in infants aged 6-11 months. 78 (56%) of 139 infants aged 6-11 months who were vaccinated developed mucosal responses against at least three of the vaccine antigens versus 14 (29%) of 49 of the infants given placebo. Addition of the adjuvant dmLT enhanced the magnitude, breadth, and kinetics (based on number of responders after the first dose of vaccine) of immune responses in infants., Interpretation: The encouraging safety and immunogenicity of ETVAX and benefit of dmLT adjuvant in young children support its further assessment for protective efficacy in children in enterotoxigenic E coli-endemic areas., Funding: PATH (Bill & Melinda Gates Foundation and the UK's Department for International Development), the Swedish Research Council, and The Swedish Foundation for Strategic Research., (Copyright © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Influenza A virus (IAV) and influenza B virus (IBV) cause substantial morbidity and mortality during seasonal epidemics. On basis of variation in the surface glycoprotein hemagglutinin, two antigenically distinct lineages of IBV are distinguished: B/Victoria/2/87-like (B/Vic) and B/Yamagata/16/88-like (B/Yam). To prevent IAV and IBV infections, both trivalent (containing IBV of one lineage) and quadrivalent (containing IBV of both lineages) influenza vaccines are used. In addition to virus-neutralizing antibodies, inactivated influenza vaccines induce antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC). Here, we determine whether vaccination with trivalent or quadrivalent inactivated influenza vaccine induces ADCC mediating antibodies directed to IBV of the two different lineages, and whether these antibodies cross-react with IBV of the opposing lineage. A robust ADCC assay based on the use of recombinant hemagglutinin and a continuous natural killer cell line that expresses FcγRIII (CD16) was used to detect the presence of ADCC mediating antibodies. Paired pre- and post-vaccination serum samples from 26 and 15 study subjects that received a trivalent or quadrivalent inactivated influenza vaccine, respectively, were assessed for the presence of ADCC mediating antibodies specific for HA derived from viruses of the B/Vic or B/Yam-lineage. Furthermore, the relative contribution of HA1- and HA2-subunit-specific antibodies to the ADCC response was determined. We found that seasonal inactivated influenza vaccines induce HA-head- and HA-stalk-specific antibodies that mediate ADCC. As expected, the quadrivalent vaccine induced antibodies to HA from both IBV lineages. Notably, a trivalent vaccine containing HA from the B/Vic lineage induced antibodies that cross-react with the B/Yam lineage., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Intranasal influenza vaccines may provide protective efficacy by inducing both systemic antibodies and local secretory IgA. Live attenuated intranasal vaccines are not feasible for high-risk groups. A previously constructed inactivated vaccine with adjuvant revealed an association with neurological events in some studies. In this phase II trial, we aimed to evaluate the safety and immunogenicity of an intranasal influenza vaccine with a novel adjuvant, heat-labile enterotoxin (LT)-derived from E. coli (LTh(αK))., Methods: This study is a multicenter, randomized controlled, double-blind, phase II trial of an intranasal influenza vaccine containing 22.5 μg of the hemagglutinin (HA) antigen of three influenza strains in combination with 2 different LTh(αK) adjuvant doses (group 1: 30 μg; group 2: 45 μg) in subjects 20-70 years old. The control vaccine was 22.5 μg of influenza HA antigen alone (group 3). The vaccine was intranasally administered on days 1 and 8. Serum anti-HA antibody and nasal secretory IgA were measured, and adverse events (AEs) were recorded prevaccination and 29 (±2) days postvaccination., Results: Of 354 participants randomized in the study, 340 received two vaccine doses. AEs were mostly mild, and there was no discontinuation related to the vaccine. Only a higher frequency of diarrhea after the first dose was noted among group 2 (11.5%) than among group 3 (2.8%), and there was no significant difference after the second dose. The three groups had comparable serum anti-HA antibody immunogenicity. However, the adjuvanted vaccines induced greater mucosal IgA antibody production than the control vaccine. In a subgroup analysis, group 1 participants achieved adequate immunogenicity among both 20- to 60- and 61- to 70-year-old participants., Conclusion: The intranasal influenza vaccine adjuvanted with LTh(αK) is generally safe and could provide systemic and local antibody responses. Adjuvanted vaccines were significantly more immunogenic than the nonadjuvanted control vaccine in mucosal immunity. ClinicalTrials.gov Identifier: NCT03784885., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: The emergence and spread of highly pathogenic avian influenza (H5N1) viruses have raised global concerns of a possible human pandemic, spurring efforts towards H5N1 influenza vaccine development and improvements in vaccine administration methods. We previously showed that a prime-boost vaccination strategy induces robust and broadly cross-reactive antibody responses against the hemagglutinin globular head domain. Here, we specifically measure antibodies against the conserved hemagglutinin stem region in serum samples obtained from the prior study to determine whether stalk-reactive antibodies can also be induced by the prime-boost regimen., Method: Serum samples collected from 60 participants before vaccination and on days 7, 28 and 90 following boosting vaccination were used in this study. 40 participants received two doses of live attenuated H5N2 vaccine (LAIV H5N2) followed by one dose of inactivated H5N1 vaccine a year later, while 20 participants received only the inactivated H5N1 vaccine. We tested these serum samples for stalk-reactive antibodies via enzyme-linked immunosorbent (ELISA) and microneutralization assays., Results: Stalk-specific antibody levels measured by both assays were found to be significantly higher in primed individuals than the unprimed group. ELISA results showed that 22.5, 70.5 and 57.5% of primed participants had a four-fold or more increase in stalk antibody titers on days 7, 28 and 90 following boosting vaccination, respectively; whereas the unprimed group had no increase. Peak geometric mean titers (GMT) for stalk antibodies in the LAIV H5N2 experienced group (24,675 [95% CI; 19,531-31,174]) were significantly higher than those who received only the inactivated H5N1 vaccine (8877 [7140-11,035]; p < 0·0001). Moreover, stalk antibodies displaying neutralizing activity also increased in primed participants, but not in the unprimed group., Conclusion: Our finding emphasizes the importance of prime-boost vaccination for effectively inducing stalk antibodies, which is an attractive target for developing vaccines that induce stalk reactive antibodies., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The occurrence of severe outbreaks of highly pathogenic avian influenza in Korea led to establishment of a national antigen bank for emergency preparedness. Here, we developed five vaccines for this bank (clade 2.3.2.1C, clade 2.3.4.4A, B, C, and D) by reverse genetics, inactivated them with formalin, and evaluated the protective efficacy and potency of serial dilutions against lethal homologous challenge in specific-pathogen-free chickens. After vaccination with one dose, each vaccine resulted in 100% survival, with no clinical symptoms, or lack of detectable virus shedding, and high levels of pre-challenge protective immunity (8.4-10.2 log 2 ). After vaccination with one-tenth of the full dose, protection was similar to that with the full dose. After vaccination with one-hundredth of the initial dose, survival was 20-80%, and all vaccines showed virus shedding. Four vaccines (excluding clade 2.3.2.1C) had satisfactory potency. In antibody-persistence tests, all vaccines maintained long-lasting protective immunity. Our results suggest that inactivated reverse-genetics vaccines genetically matched to outbreak viruses provide adequate protection after a single vaccination., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Influenza A viruses cause major morbidity and represent a severe global health problem. Current influenza vaccines are mainly egg-based products requiring the split of whole viruses using classical detergents such as Triton X-100, which implies certain limitations. Here, we report the use of the novel calixarene-based surfactant CALX133ACE as an alternative to classical detergents for influenza inactivated split vaccine preparation. We confirmed that CALX133ACE-based split HA antigens are fully functional and quantifiable by the "gold standard" method SRID. Additionally, as in the case of the Triton X-100-based split, the CALX133ACE-based split antigens are stable for at least 6 months at 4 °C. Moreover, immunization of mice with CALX133ACE-based split NYMC X-179A (H1N1) antigens harboring 10 to 30-fold less antigen than the commercialized trivalent inactivated vaccines Vaxigrip® or Fluviral® induced comparable efficient protection and neutralizing antibody responses against A(H1N1)pdm09 infection. Taken together, our results demonstrate for the first time the use of a calixarene-based detergent as an efficient splitting agent for the production of optimized influenza split antigens, paving the way for significant improvement in the vaccine manufacturing process, notably with regard to the current regulation on the prohibition of endocrine disruptors, such as Triton X-100., (Copyright © 2019. Published by Elsevier Ltd.)

Background: Influenza viruses cause substantial annual morbidity and mortality globally. Current vaccines protect against influenza only when well matched to the circulating strains. However, antigenic drift can cause considerable mismatches between vaccine and circulating strains, substantially reducing vaccine effectiveness. Moreover, current seasonal vaccines are ineffective against pandemic influenza, and production of a vaccine matched to a newly emerging virus strain takes months. Therefore, there is an unmet medical need for a broadly protective influenza virus vaccine. We aimed to test the ability of chimeric H1 haemagglutinin-based universal influenza virus vaccine candidates to induce broadly cross-reactive antibodies targeting the stalk domain of group 1 haemagglutinin-expressing influenza viruses., Methods: We did a randomised, observer-blinded, phase 1 study in healthy adults in two centres in the USA. Participants were randomly assigned to one of three prime-boost, chimeric haemagglutinin-based vaccine regimens or one of two placebo groups. The vaccine regimens included a chimeric H8/1, intranasal, live-attenuated vaccine on day 1 followed by a non-adjuvanted, chimeric H5/1, intramuscular, inactivated vaccine on day 85; the same regimen but with the inactivated vaccine being adjuvanted with AS03; and an AS03-adjuvanted, chimeric H8/1, intramuscular, inactivated vaccine followed by an AS03-adjuvanted, chimeric H5/1, intramuscular, inactivated vaccine. In this planned interim analysis, the primary endpoints of reactogenicity and safety were assessed by blinded study group. We also assessed anti-H1 haemagglutinin stalk, anti-H2, anti-H9, and anti-H18 IgG antibody titres and plasmablast and memory B-cell responses in peripheral blood. This trial is registered with ClinicalTrials.gov, number NCT03300050., Findings: Between Oct 10, 2017, and Nov 27, 2017, 65 participants were enrolled and randomly assigned. The adjuvanted inactivated vaccine, but not the live-attenuated vaccine, induced a substantial serum IgG antibody response after the prime immunisation, with a seven times increase in anti-H1 stalk antibody titres on day 29. After boost immunisation, all vaccine regimens induced detectable anti-H1 stalk antibody (2·2-5·6 times induction over baseline), cross-reactive serum IgG antibody, and peripheral blood plasmablast responses. An unsolicited adverse event was reported for 29 (48%) of 61 participants. Solicited local adverse events were reported in 12 (48%) of 25 participants following prime vaccination with intramuscular study product or placebo, in 12 (33%) of 36 after prime immunisation with intranasal study product or placebo, and in 18 (32%) of 56 following booster doses of study product or placebo. Solicited systemic adverse events were reported in 14 (56%) of 25 after prime immunisation with intramuscular study product or placebo, in 22 (61%) of 36 after immunisation with intranasal study product or placebo, and in 21 (38%) of 56 after booster doses of study product or placebo. Disaggregated safety data were not available at the time of this interim analysis., Interpretation: The tested chimeric haemagglutinin-based, universal influenza virus vaccine regimens elicited cross-reactive serum IgG antibodies that targeted the conserved haemagglutinin stalk domain. This is the first proof-of-principle study to show that high anti-stalk titres can be induced by a rationally designed vaccine in humans and opens up avenues for further development of universal influenza virus vaccines. On the basis of the blinded study group, the vaccine regimens were tolerable and no safety concerns were observed., Funding: Bill & Melinda Gates Foundation., (Copyright © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

There is an urgent need for efficient vaccines against the highly pathogenic avian influenza A viral strain H7N9. The duration and intensity of the immune response to H7N9 critically impacts the epidemiology of influenza viral infection at the population level. However, the insufficient immunogenicity of H7N9 raises concerns about vaccine efficacy. In this study, we evaluated the impact of immunization routes and the adjuvant CpG on the immune response to a split H7N9 vaccine in mice. Determination of humoral and cellular responses to the vaccine revealed that after four vaccine doses, high titers of H7N9-specific serum IgG, determined by the influenza hemagglutination inhibition (HI) assay, were induced through the intramuscular (i.m.) route and lasted for at least 40 weeks. CpG-adjuvanted immunization increased the levels of long-lived IFN-γ + T cells and raised the Th1-biased IgG2a/IgG1 response ratio. In addition, aside from mucosal IgA, CpG-adjuvanted intranasal (i.n.) immunization elicited serum IgG and cellular responses of a similar duration and intensity to CpG-adjuvanted i.m. immunization. Mouse challenge assays demonstrated that 24 weeks following i.m. immunization without CpG or CpG-adjuvanted immunization through the i.m. or i.n. routes, both offered a high level of protection against H7N9 infection. These results indicate that efficient long-term protection against H7N9 can be achieved via the optimization of vaccination strategies, such as immunization doses, routes, and adjuvants., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In recent years, cell-based influenza vaccines have gained a great interest over the egg-based vaccines. Several inactivated H7N9 vaccines have been evaluated in clinical trials, including whole-virion vaccines, split vaccines and subunit vaccines. Recently, we developed a new suspension MDCK (sMDCK) cell line for influenza viruses production. However, the properties of purified antigen from sMDCK cells remain unclear. In this study, the stability of influenza H7N9 vaccine bulk derived from sMDCK cells was investigated, and the data were compared with the vaccine antigen derived from our characterized adhesion MDCK (aMDCK) cells in serum-free medium. The influenza H7N9 bulks derived from sMDCK and aMDCK cells were stored at 2-8 °C for different periods of time, and a number of parameters selected to monitor the H7N9 vaccine antigen stability were evaluated at each interval (1, 3 and 12 months). The monitored parameters included virus morphology, hemagglutinin (HA) activity, HA concentration, antigenicity, and immunogenicity. The sMDCK-derived H7N9 bulk showed similar morphology to that of the aMDCK-derived H7N9 bulk, and there were no obvious changes after the extended storage periods. Furthermore, the HA titer, HA concentration, and antigenicity of sMDCK-derived H7N9 bulk were stable after 28 months of storage. Finally, the results of hemagglutination inhibition and neutralization tests showed that sMDCK- and aMDCK-derived H7N9 vaccines had comparable immunogenicity. These results indicated that sMDCK-derived H7N9 bulk has good stability compared to that of aMDCK-derived H7N9 bulk. Thus, the newly developed suspension MDCK cell line shows a great alternative for manufacturing cell-based influenza vaccines., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Variations in the composition of commensal gut microbiota have been reported to be major contributors to differences in responses to vaccination among individuals. In chickens, there is limited information on the role of gut microbiota in responses to vaccination. The current study studied the role of gut microbiota in cell- and antibody-mediated immune responses to vaccination with a whole inactivated avian influenza virus, subtype H9N2. A total of 166 one-day-old specific pathogen free layer chickens (SPF) were randomly assigned to treatments, where a combination of antibiotic depletion, and probiotics (a combination of five Lactobacillus species) or fecal microbial transplant (FMT) reconstitution were used to study the dynamics of cell- and antibody-mediated immune responses to primary and secondary vaccinations at days 15 and 29 of age, respectively. Overall, at days 7 and 14 post primary vaccination (p.p.v.), administration of probiotics to non-depleted chickens resulted in significantly higher mean hemagglutination (HI) titre compared to antibiotic treated chickens. Furthermore, at day 21 p.p.v., chickens treated with probiotics or FMT post-antibiotic treatment showed a significantly higher mean HI titre compared to non-depleted chickens treated with probiotics. At day 7 p.p.v., a significantly higher virus specific IgM and IgG titres were observed in non-depleted chickens administered with probiotics compared to antibiotic depleted chickens, and a significantly higher IgG titre was observed in chickens treated with FMT following antibiotic treatment compared to only antibiotic treatment. Analysis of interferon gamma expression in splenocytes to assess cell-mediated immune responses showed a significantly lower expression in antibiotic-treated chickens compared to non-depleted chickens and FMT reconstituted chickens. Taken together, the current study suggests that shifts in the composition of gut microbiota of chickens may result in changes in cell- and antibody-mediated immune responses to vaccination against influenza viruses. Further studies will be needed to highlight the mechanisms involved in this modulation., (Copyright © 2019. Published by Elsevier Ltd.)

The adjuvant CVC1302 was previously shown to efficiently enhance the immunogenicity of killed foot-and-mouth disease virus (FMDV) in mice and piglets. However, the underlining mechanism of action of CVC1302 remains unclear, especially at local injection sites and draining lymph nodes. Since the FMDV vaccine is administrated intramuscularly in field settings, we studied local immune responses to FMDV following intramuscular injection in mice, and found that CVC1302-adjuvanted killed FMDV (KV-CVC1302) induced secretion of several chemokines in murine muscle tissues, including MCP-1, MIP-1α, and MIP-1β. The number of monocytes recruited to the site of injection was significantly higher in mice immunized with KV-CVC1302 compared with mice immunized with killed FMDV alone (KV). iTAQ-based quantitative proteomic assays were additionally employed to explore the molecular mechanisms of CVC1302 action in the draining lymph nodes. A total of 35 proteins were identified as being differentially expressed among the control group, KV-immunized group and KV-CVC1302-immunized group at 10 days post immunization (dpi). Proteins exhibiting differential expression were mainly involved in signal transduction, apoptosis, endocytosis and innate immune responses. Pathway analysis demonstrated that AMPK, phospholipase D, cAMP, Rap1, and MAPK signaling pathways were potentially induced by the immunopotentiator CVC1302. Understanding the local mechanism of CVC1302 action at injection sites and draining lymph nodes will provide new insights into the development of FMDV vaccines., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Type B Coxsackieviruses (CVBs) belong to the enterovirus genus, and they cause both acute and chronic diseases in humans. CVB infections usually lead to flu-like symptoms but can also result in more serious diseases such as myocarditis, aseptic meningitis and life-threatening multi-organ infections in young infants. Thus, CVBs have long been considered as important targets of future vaccines. We have previously observed CVB1 capsid disintegration and virus concentration decrease with 12-day long formalin inactivation protocol. Here a scalable ion exchange chromatography purification method was developed, and purified CVB1 was inactivated with UV-C or formalin. Virus morphology and concentration remained unchanged, when the UV (2 min) or formalin (5 days) inactivation were performed in the presence of tween80 detergent. The concentration of the native and UV inactivated CVB1 remained constant at 4 °C during a six months stability study, whereas the concentration of the formalin inactivated vaccine decreased 29% during this time. UV treatment decreased, whereas formalin treatment increased the thermal stability of the capsid. The formalin inactivated CVB1 vaccine was more immunogenic than the UV inactivated vaccine; the protective neutralizing antibody levels were higher in mice immunized with formalin inactivated vaccine. High levels of CVB1 neutralizing antibodies as well as IgG1 antibodies were detected in mice that were protected against viremia induced by experimental CVB1 infection. In conclusion, this study describes a scalable ion exchange chromatography purification method and optimized 5-day long formalin inactivation method that preserves CVB1 capsid structure and immunogenicity. Formalin treatment stabilizes the virus particle at elevated temperatures, and the formalin inactivated vaccine induces high levels of serum IgG1 antibodies (Th2 type response) and protective levels of neutralizing antibodies. Formalin inactivated CVB vaccines are promising candidates for human clinical trials., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)