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Background: Influenza A (H7N9) has caused multiple disease waves with evidence of strain diversification. Optimal influenza A (H7N9) prime-boost vaccine strategies are unknown., Methods: We recruited participants who had received monovalent inactivated A/Shanghai/2/2013 (H7N9) vaccine (MIV) approximately 5 years earlier, as follows: MIV with MF59 (MF59 × 2 group), MIV with AS03 (AS03 × 2 group), unadjuvanted MIV (No Adj group), MIV with MF59 or AS03 followed by unadjuvanted MIV (Adjx1 group), and A/H7-naive (unprimed group). Participants were randomized to receive 1 dose of AS03-adjuvanted or unadjuvanted A/Hong Kong/125/2017 (H7N9) MIV and were followed for safety and immunogenicity using hemagglutination inhibition (HAI) and neutralizing antibody assays., Results: We enrolled 304 participants: 153 received the adjuvanted boost and 151 received the unadjuvanted boost. At 21 days postvaccination, the proportion of participants with HAI antibody titers against the boosting vaccine strain of ≥40 in the adjuvanted and unadjuvanted arms, respectively, were 88% and 49% in MF59 × 2 group, 89% and 75% in AS03 × 2 group, 59% and 20% in No Adj group, 94% and 55% in Adjx1group, and 9% and 11% in unprimed group., Conclusions: Serologic responses to a heterologous A(H7N9) MIV boost were highest in participants primed and boosted with adjuvant-containing regimens., Clinical Trials Registration: NCT03738241., Competing Interests: Potential conflicts of interest . I. Y.’s institution received funding to conduct clinical research unrelated to this manuscript from Moderna and Pfizer; and I. Y. consults for Merck and Sanofi-Pasteur. P. W. has received research funding unrelated to this manuscript from Pfizer and Sanofi; and has consulted for Pfizer. C. B. C. serves as a consultant to Pfizer, Moderna, GSK, and Vir. K. M. E. serves as consultant to Bionet and IBM; and member of the Data Safety and Monitoring Boards for Sanofi, X-4 Pharma, Seqirus, Moderna, Pfizer, Merck, and Roche. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Human infections with the avian influenza A(H7N9) virus were first reported in China in 2013 and continued to occur in annual waves. In the 2016/2017 fifth wave, Yangtze River Delta (YRD) lineage viruses, which differed antigenically from those of earlier waves, predominated., Methods: In this phase 2 double-blinded trial we randomized 720 adults ≥ 19 years of age to receive two injections of a YRD lineage inactivated A/Hong Kong/125/2017 fifth-wave H7N9 vaccine, given 21 days apart, at doses of 3.75, 7.5, and 15 µg of hemagglutinin (HA) with AS03A adjuvant and at doses of 15 and 45 µg of HA without adjuvant., Results: Two doses of adjuvanted vaccine were required to induce HA inhibition (HI) antibody titers ≥ 40 in most participants. After two doses of the 15 µg H7N9 formulation, given with or without AS03 adjuvant, the proportion achieving a HI titer ≥ 40 against the vaccine strain at 21 days after the second vaccination was 65 % (95 % CI, 57 %-73 %) and 0 % (95 % CI, 0 %-4%), respectively. Among those who received two doses of the 15 µg adjuvanted formulation the proportion with HI titer ≥ 40 at 21 days after the second vaccination was 76 % (95 % CI, 66 %-84 %) in those 19-64 years of age and 49 % (95 % CI, 37 %-62 %) in those ≥ 65 years of age. Responses to the adjuvanted vaccine formulations did not vary by HA content. Antibody responses declined over time and responses against drifted H7N9 strains were diminished. Overall, the vaccines were well tolerated but, as expected, adjuvanted vaccines were associated with more frequent solicited systemic and local adverse events., Conclusions: AS03 adjuvant improved the immune responses to an inactivated fifth-wave H7N9 influenza vaccine, particularly in younger adults, but invoked lower responses to drifted H7N9 strains. These findings may inform future influenza pandemic preparedness strategies., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [LAJ reports funding support to her institution from Pfizer for the conduct of a clinical trial of an investigational influenza vaccine. NGR is a paid safety consultant for ICON and EMMES, serves on the advisory boards for GSK, Moderna, Sanofi, and Seqirus and her institution received funds for the conduct of research from Sanofi, Lilly, Merck, Quidel, and Pfizer. MJM reported potential competing interests: laboratory research and clinical trials contract funding with Lilly, Pfizer, and Sanofi; personal fees for Scientific Advisory Board service from Merck, Meissa Vaccines, Inc. and Pfizer. EBW has received funding support from Pfizer, Moderna, Sequiris, Najit Technologies Inc, and Clinetic for the conduct of clinical trials and clinical research and has served as an advisor to Vaxcyte and consultant to ILiAD biotechnologies. CAR.’s institution has received funds to conduct clinical research unrelated to this manuscript from BioFire Inc, GSK, MedImmune, Micron, Janssen, Merck, Moderna, Novavax, PaxVax, Pfizer, Regeneron, Sanofi-Pasteur. She is co-inventor of patented RSV vaccine technology unrelated to this manuscript, which has been licensed to Meissa Vaccines, Inc.]., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Influenza A/H7N9 viruses have pandemic potential., Methods: We conducted an open-label, randomized, controlled trial of AS03-adjuvanted 2017 inactivated influenza A/H7N9 vaccine (H7N9 IIV) in healthy adults. Group 1 received H7N9 IIV and seasonal quadrivalent influenza vaccine (IIV4) simultaneously, followed by H7N9 IIV three weeks later. Group 2 received IIV4 alone and then two doses of H7N9 IIV at three-week intervals. Group 3 received one dose of IIV4. We used hemagglutination inhibition (HAI) and microneutralization (MN) assays to measure geometric mean titers and seroprotection (≥1:40 titer) to vaccine strains and monitored for safety., Results: Among 149 subjects, seroprotection by HAI three weeks after H7N9 IIV dose 2 was 51% (95 %CI 37%-65%) for Group 1 and 40% (95 %CI 25%-56%) for Group 2. Seroprotection by MN at the same timepoint was 84% (95 %CI 72%-93%) for Group 1 and 74% (95 %CI 60%-86%) for Group 2. By 180 days after H7N9 IIV dose 2, seroprotection by HAI or MN was low for Groups 1 and 2. Responses measured by HAI and MN against each IIV4 strain three weeks after IIV4 vaccination were similar in all groups. Solicited local and systemic reactions were similar after a single vaccination, while those receiving simultaneous H7N9 and IIV4 had slightly more reactogenicity. There were no serious adverse events or medically-attended adverse events related to study product receipt., Conclusions: Adjuvanted H7N9 IIV was modestly immunogenic whether administered simultaneously or sequentially with IIV4, though responses declined by 180 days. IIV4 was immunogenic regardless of schedule., Clinical Trials Registration: NCT03318315., 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 © 2022 Elsevier Ltd. All rights reserved.)

Background: Influenza vaccination is uncommon in low-resource settings. We evaluated aspects of operational feasibility of influenza vaccination programs targeting risk groups in the World Health Organization (WHO) African (AFR) and South-East Asian (SEAR) Regions., Methods: We estimated routine immunization and influenza vaccination campaign doses, doses per vaccinator, and cold storage requirements for 1 simulated country in each region using evidence-based population distribution, vaccination schedule, and vaccine volumes. Influenza vaccination targeted persons <5 years, pregnant women, persons with chronic diseases, persons ≥65 years, and healthcare workers (HCW). For the AFR country, we compared vaccine volumes to actual storage capacities., Results: Targeting HCW had a small operational impact, and subsequent findings exclude this group. During 3-month influenza vaccination campaigns, monthly doses delivered in the AFR country increased from 15.0% for ≥65 years to 93.1% for <5 years and in the SEAR country from 19.6% for pregnant women to 145.0% for persons with chronic diseases. National-level cold storage capacity requirements increased in the AFR country from 4.1% for ≥65 years to 20.3% for <5 years and in the SEAR country from 3.9% for pregnant women to 28.8% for persons with chronic diseases. Subnational-level cold storage capacity requirements increased in the AFR country from 5.9% for ≥65 years to 36.8% for <5 years and the SEAR country from 17.6% for pregnant women to 56.0% for persons with chronic diseases., Conclusions: Influenza vaccination of most risk groups will require substantial increases in doses, doses per vaccinator, and cold storage capacity in countries where infrastructure and resources are limited., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: The number of human influenza A (H7N9) infections has escalated since 2013 with high resultant mortality. We conducted a phase II, randomized, partially-blinded trial to evaluate the safety and immunogenicity of an MF59-adjuvanted inactivated, split virion, H7N9 influenza vaccine (H7N9 IIV) administered at various dose levels and schedules in older adults., Methods: 479 adults ≥ 65 years of age in stable health were randomized to one of six groups to receive either 3.75, 7.5 or 15 µg of influenza A/Shanghai/02/2013 (H7N9) IIV adjuvanted with MF59 given as a 3-dose series either on days 1, 28 and 168 or on days 1, 57 and 168. Immunogenicity was assessed using both hemagglutination inhibition (HAI) and microneutralization (MN) assays prior to and 28 days following each dose. Safety was assessed through 1 year following the last dose., Results: Subjects in all groups had only modest immune responses, with the HAI GMT < 20 after the second vaccine dose and <29 after the third vaccine dose. HAI titers ≥ 40 were seen in <37% of subjects after the second dose and <49% after the third dose. There were no significant differences seen between the two dose schedules. MN titers followed similar patterns, although the titers were approximately two-fold higher than the HAI titers. Logistic regression modeling demonstrated no statistically significant associations between the immune responses and age, sex or body mass index whereas recent prior receipt of seasonal influenza vaccine significantly reduced the HAI response [OR 0.13 (95% CI 0.05, 0.33); p < 0.001]. Overall, the vaccine was well tolerated. Two mild potentially immune mediated adverse events occurred, lichen planus and guttate psoriasis., Conclusions: MF59-adjuvanted H7N9 IIV was only modestly immunogenic in the older adult population following three doses. There were no significant differences in antibody responses noted among the various antigen doses or the two dose schedules., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [PLW, LAJ, KE, DIB, MJM, HES, RER, HH, SEF, KS have no conflicts of interest. WHC has consulted for Sequirus, FluGen and Pharmaron on influenza related projects.]., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The 2017-2018 influenza season reminds us that it is important for health care professionals to be prepared for the annual onslaught of this contagious respiratory disease associated with potentially serious complications. Vaccination is by far the best method to prevent and control influenza, reducing illness, hospitalizations, and mortality. The highest rates of influenza-associated morbidity and mortality are observed in older adults. The immune function of older adults decreases with increasing age, a phenomenon termed immunosenescence. Immunosenescence not only confers increased susceptibility to influenza disease, but also renders vaccination less effective. To address the need for improved vaccines that provide enhanced protection to this high-risk group, 2 formulations-a high-dose vaccine and an adjuvanted vaccine-have been approved in recent years specifically for people aged 65 years and over. Here we discuss: the challenges of influenza immunization in those 65 years and older; the recent advancements in vaccines targeted at this age group; and the latest influenza vaccine recommendations for the 2017-2018 influenza season in the United States., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Influenza A(H5N1) virus and other avian influenza virus strains represent major pandemic threats. Like all influenza A virus strains, A(H5N1) viruses evolve rapidly. Innovative immunization strategies are needed to induce cross-protective immunity., Methods: Subjects primed with clade 1 H5 antigen, with or without adjuvant, and H5-naive individuals were boosted with clade 2 H5 antigen. The impact of priming on T cells capable of both proliferation and cytokine production after antigen restimulation was assessed., Results: Subjects previously vaccinated with clade 1 H5 antigen developed significantly enhanced clade 2 H5 cross-reactive T cell responses detectable 6 months after vaccination with clade 2 H5 antigen. Priming dose (15 µg vs 45 or 90 µg) had no effect on magnitude of heterotypic H5 T cell responses. In contrast, age at priming negatively modulated both the magnitude and duration of heterotypic H5 T cell responses. Elderly subjects developed significantly less heterotypic H5 T cell boosting, predominantly for T cells capable of cytokine production. Adjuvant had a positive albeit weaker effect than age. The magnitude of CD4(+) interferon-γ producing T cells correlated with H5 antibody responses., Conclusions: H5 heterotypic priming prior to onset of an A(H5N1) pandemic may increase magnitude and duration of immunity against a newly drifted pandemic H5 virus., (© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.)

Background: Despite the heightened risk of serious influenza during infancy, vaccination is not recommended in infants younger than 6 months. We aimed to assess the safety, immunogenicity, and efficacy of maternal immunisation with trivalent inactivated influenza vaccine for protection of infants against a first episode of laboratory-confirmed influenza., Methods: We did this prospective, active-controlled, observer-blind, randomised phase 4 trial at six referral centres and community health centres in Bamako, Mali. Third-trimester pregnant women (≥28 weeks' gestation) were randomly assigned (1:1), via a computer-generated, centre-specific list with alternate block sizes of six or 12, to receive either trivalent inactivated influenza vaccine or quadrivalent meningococcal vaccine. Study personnel administering vaccines were not masked to treatment allocation, but allocation was concealed from clinicians, laboratory personnel, and participants. Infants were visited weekly until age 6 months to detect influenza-like illness; laboratory-confirmed influenza diagnosed with RT-PCR. We assessed two coprimary objectives: vaccine efficacy against laboratory-confirmed influenza in infants born to women immunised any time prepartum (intention-to-treat population), and vaccine efficacy in infants born to women immunised at least 14 days prepartum (per-protocol population). The primary outcome was the occurrence of a first case of laboratory-confirmed influenza by age 6 months. This trial is registered with ClinicalTrials.gov, number NCT01430689., Findings: We did this trial from Sept 12, 2011, to Jan 28, 2014. Between Sept 12, 2011, and April 18, 2013, we randomly assigned 4193 women to receive trivalent inactivated influenza vaccine (n=2108) or quadrivalent meningococcal vaccine (n=2085). There were 4105 livebirths; 1797 (87%) of 2064 infants in the trivalent inactivated influenza vaccine group and 1793 (88%) of 2041 infants in the quadrivalent meningococcal vaccine group were followed up until age 6 months. We recorded 5279 influenza-like illness episodes in 2789 (68%) infants, of which 131 (2%) episodes were laboratory-confirmed influenza. 129 (98%) cases of laboratory-confirmed influenza were first episodes (n=77 in the quadrivalent meningococcal vaccine group vs n=52 in the trivalent inactivated influenza vaccine group). In the intention-to-treat population, overall infant vaccine efficacy was 33·1% (95% CI 3·7-53·9); in the per-protocol population, vaccine efficacy was 37·3% (7·6-57·8). Vaccine efficacy remained robust during the first 4 months of follow-up (67·9% [95% CI 35·1-85·3] by intention to treat and 70·2% [35·7-87·6] by per protocol), before diminishing during the fifth month (57·3% [30·6-74·4] and 60·7 [33·8-77·5], respectively). Adverse event rates in women and infants were similar among groups. Pain at the injection site was more common in women given quadrivalent meningococcal vaccine than in those given trivalent inactivated influenza vaccine (n=253 vs n=132; p<0·0001), although 354 [92%] reactions were mild. Obstetrical and non-obstetrical serious adverse events were reported in 60 (3%) women in the quadrivalent meningococcal vaccine group and 61 (3%) women in the trivalent inactivated influenza vaccine group. Presumed neonatal infection was more common in infants in the trivalent inactivated influenza vaccine group than in those in the quadrivalent meningococcal vaccine group (n=60 vs n=37; p=0·02). No serious adverse events were related to vaccination., Interpretation: Vaccination of pregnant women with trivalent inactivated influenza vaccine in Mali-a poorly resourced country with high infant mortality-was technically and logistically feasible and protected infants from laboratory-confirmed influenza for 4 months. With adequate financing to procure the vaccine, implementation will parallel the access to antenatal care and immunisation coverage of pregnant women with tetanus toxoid., Funding: Bill & Melinda Gates Foundation., (Copyright © 2016 Tapia et al. Open Access article distributed under the terms of CC BY. Published by Elsevier Ltd.. All rights reserved.)

Purpose: The study aims were to determine whether inactivated influenza A/H5N1 vaccine administration elicited cell mediated immune (CMI) responses and the impact of adjuvant, vaccine dose and subject age on these responses., Methods: Adults who were previously primed with either adjuvanted or unadjuvanted, inactivated, A/H5N1/Vietnam/1203/2004 (Clade 1) vaccine or unprimed (received placebo) in previous vaccine studies were randomized to receive one (primed) or two (unprimed) 15- or 90-mcg doses of inactivated, A/H5N1/Indonesia/05/05 (Clade 2) vaccine. Peripheral blood mononuclear cells (PBMCs) were collected and analyzed from a subset of vaccinees to assess CMI responses using IFN-γ and granzyme B ELISPOT assays. Cytokine measurements were performed on PBMC supernatants after stimulation with H5N1 virus., Results: PBMCs were available from 177 participants; 88 and 89 received 15-mcg and 90-mcg of unadjuvanted clade 2 vaccine, respectively. Following H5N1 clade 1 stimulation, IFN-γ but not granzyme B normalized spot-forming cell numbers had statistically significant increased numbers at each of the post-vaccination timepoints compared to baseline in pooled analyses of all vaccine doses and age groups. Clade 2 stimulation resulted in statistically significant increased numbers of IFN-γ cells only 180 days following the last vaccination. Responses were similar among younger and older study participants, as were responses among those primed with alum-adjuvanted or non-adjuvanted clade 1 H5N1 vaccines. The dosage of clade 2 vaccine did not impact CMI responses among primed subjects, but responses were statistically significantly greater in unprimed recipients of the 90-mcg dosage compared to unprimed recipients of the 15-mcg dosage. IFN-γ levels in the supernatants of stimulated PBMC were strongly correlated with IFN-γ ELISPOT results., Conclusion: CMI responses occur in adults administered influenza A/H5N1 inactivated influenza vaccine., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The adjuvant AS03 is stockpiled for future formulations with new and existing vaccines for the control of pandemic influenza virus. We previously reported the immunogenicity of an A/H5N1 vaccine extemporaneously mixed with the AS03 adjuvant for 42 days following vaccination. This report extends those findings to 1 year after vaccination., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Influenza A(H5N1) vaccination strategies that improve the speed of the immunological response and cross-clade protection are desired. We compared the immunogenicity of a single 15-μg or 90-μg dose of A/H5N1/Indonesia/05/05 (clade 2) vaccine in adults who were previously primed with A/H5N1/Vietnam/1203/2004 (clade 1) vaccine. High-dose vaccine resulted in significantly higher titers to both clade 1 and 2 antigens. Clade 2 titers were unaffected by the previous dose of clade 1 vaccine. Low-dose priming with a mismatched pandemic influenza A(H5N1) vaccine would improve the rapidity, magnitude, and cross-reactivity of the immunological response following a single high-dose, unadjuvanted, pandemic vaccine., (© The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Importance: The need to respond quickly to potential influenza pandemics is important. Immunologic priming (initial presentation of an antigen to allow antibody responses on revaccination) with vaccine directed toward an older avian influenza H5 strain might lead to secondary antibody responses to a single dose of more current H5 avian influenza vaccine., Objectives: To assess priming with the older avian influenza A/Vietnam/1203/2004(H5N1) (Vietnam) vaccine and to conduct dose-response studies with vaccine directed against the more contemporary H5N1 avian influenza virus, influenza A/Anhui/01/2005 (Anhui)., Design, Setting, and Participants: Multicenter US randomized clinical trial beginning in June 2010 with follow-up continuing through October 2011 enrolling 72 healthy adults who were vaccinated 1 year previously with the Vietnam vaccine and 565 vaccine-naive adults., Interventions: Participants who were previously vaccinated with 90 µg of unadjuvanted Vietnam vaccine were randomly assigned to receive 3.75 µg of avian influenza Anhui vaccine with or without MF59 adjuvant, stratified by 1 vs 2 previous doses (1 dose: n = 18 with MF59 and n = 17 without; 2 doses: n = 19 with MF59 and n = 18 without). Vaccine-naive individuals were randomly assigned to receive Ahnui vaccine with or without MF59 adjuvant in 1 of 5 doses (3.75 µg [n = 55 with MF59 and n = 59 without], 7.5 µg [n = 51 with MF59 and n = 57 without], 15 µg [n = 48 with MF59 and n = 44 without], 45 µg [n = 47 with MF59 and n = 47 without], or 90 µg [n = 57 without adjuvant]) or placebo (n = 100) given at days 0 and 28., Main Outcomes and Measures: The primary immunogenicity outcome was hemagglutination inhibition assay (HAI) titer against each vaccine antigen 1 month (day 28) and 6 months (day 180) after last vaccination. The primary safety outcomes were local and systemic adverse events on days 0 to 7 after each vaccination and serious adverse events., Results: Previously vaccinated participants manifested secondary antibody responses after receipt of low-dose Anhui vaccine ("boosting"); by day 28, 21% to 50% developed HAI responses of 1:40 or greater. Use of adjuvant was not associated with increased HAI responses. Among vaccine-naive participants (n = 565), the optimum dose was 7.5 µg of antigen with adjuvant (geometric mean titer [GMT], 63.3; 95% CI, 43.0-93.1). The greatest response to unadjuvanted antigen was seen at the highest dose, 90 µg (GMT, 28.5; 95% CI, 19.7-41.2). Local or systemic reactions occurred, respectively, in 40 (78%) and 25 (49%) of 51 participants who received 7.5 µg plus adjuvant vs 50 (88%) and 29 (51%) of 57 who received 90 µg of unadjuvanted vaccine. In general, antibodies were short-lived, and by day 180, HAI titers had decreased to less than 1:20 in all treatment groups., Conclusions and Relevance: Previous receipt of a single dose of influenza A(H5N1) Vietnam vaccine was associated with sufficient immunologic priming to facilitate antibody response to a different H5N1 antigen using low-dose Anhui (booster) vaccine. In participants who had not previously received H5 vaccine, low-dose Anhui vaccine plus adjuvant was more immunogenic compared with higher doses of unadjuvanted vaccine., Trial Registration: clinicaltrials.gov Identifier: NCT00680069.

Background: Adjuvanted vaccines have the potential to improve influenza pandemic response. AS03 adjuvant has been shown to enhance the immune response to inactivated influenza vaccines., Methods: This trial was designed to evaluate the immunogenicity and safety of an inactivated 2009 H1N1 influenza vaccine at varying dosages of hemagglutinin with and without extemporaneously mixed AS03 adjuvant system in adults ≥ 18 years of age. Adults were randomized to receive 2 doses of 1 of 5 vaccine formulations (3.75 µg, 7.5 µg, or 15 µg with AS03 or 7.5 µg or 15 µg without adjuvant)., Results: The study population included 544 persons <65 years of age and 245 persons ≥ 65 years of age. Local adverse events tended to be more frequent in the adjuvanted vaccine groups, but severe reactions were uncommon. In both age groups, hemagglutination inhibition antibody geometric mean titers after dose one were higher in the adjuvanted groups, compared with the 15 µg unadjuvanted group, and this difference was statistically significant for the comparison of the 15 µg adjuvanted group with the 15 µg unadjuvanted group., Conclusions: AS03 adjuvant system improves the immune response to inactivated 2009 H1N1 influenza vaccine in both younger and older adults and is generally well tolerated. ClinicalTrials.gov NCT00963157.

Background: The influenza A/H1N1 pandemic in 2009 created an urgent need to develop vaccines for mass immunization. To guide decisions regarding the optimal immunization dosage and schedule for adults, we evaluated two monovalent, inactivated, unadjuvanted H1N1 influenza vaccines in independent, but simultaneously conducted, multi-center Phase 2 trials of identical design., Methods: Healthy adults, stratified by age (18-64 years and ≥65 years), were randomized (1:1 allocation), in a double-blind, parallel-group design, to receive two intramuscular doses (21 days apart) of vaccine containing approximately 15 μg or 30 μg of hemagglutinin (HA). Primary endpoints were safety (reactogenicity for 8 days after each vaccination and vaccine-associated serious adverse events during the 7 month study) and immunogenicity (proportion of subjects, stratified by age, achieving a serum hemagglutination inhibition [HI] antibody titer ≥1:40 or a ≥4-fold rise in titer after a single injection of either dosage)., Results: Both vaccines were well-tolerated. A single 15 μg dose induced HI titers ≥1:40 in 90% of younger adults (95% confidence interval [CI] 82-95%) and 81% of elderly (95% CI 71-88%) who received Sanofi-Pasteur vaccine (subsequently found to contain 24 μg HA in the standard potency assay), and in 80% of younger adults (95% CI 71-88%) and 60% of elderly (95% CI 50-70%) who received CSL vaccine. Both vaccines were significantly more immunogenic in younger compared with elderly adults by at least one endpoint measure. Increasing the dose to 30 μg raised the frequency of HI titers ≥1:40 in the elderly by approximately 10%. Higher dosage did not significantly enhance immunogenicity in younger adults and a second dose provided little additional benefit to either age group., Conclusion: These trials provided evidence for policymakers that a single 15 μg dose of 2009 A/H1N1 vaccine would likely protect most U.S. adults and suggest a potential benefit of a 30 μg dose for the elderly., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A comparative analysis of antibody and cell-mediated immune responses was performed in ambulatory medically stable elderly and young adults who received the standard-dose of trivalent inactivated influenza vaccine, containing 15 μg of hemagglutinin (HA) per virus strain, or a high-dose vaccine containing 60 μg HA per virus strain. Among the elderly, the high dose vaccine induced greater HAI (hemagglutination inhibition) and virus neutralization antibody titers than the standard dose vaccine. These responses, however, did not achieve the magnitude of those induced by the standard dose vaccine in young adults. Vaccine-specific circulating T cells producing IFN-γ were detected in the elderly and young adults following immunization. However, there were no significant differences in the IFN-γ responses among groups. On the other hand, the standard dose vaccine in the elderly resulted in the highest proportion of complete non-responders who failed to elicit either an HAI or an IFN-γ response. This study provides further evidence that a higher dose vaccine for the elderly may result in enhanced immune responses which are predicted to improve protection although still of lower magnitude than those induced in younger healthier individuals., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Antibody to the neuraminidase (NA) antigen of influenza viruses has been shown to correlate with immunity to influenza in humans and animal models. In a previous report, we showed that an inactivated influenza vaccine containing 60microg of the hemagglutinin (HA) of each strain induced significantly more serum anti-HA antibody among elderly persons than did the standard vaccine containing 15microg of the HA of each component. We developed a lectin-based assay for anti-NA antibody and used it to measure anti-NA antibody responses among subjects who had participated in that study. The high dosage vaccine contained eight times as much NA activity as the standard vaccine and induced a significantly higher frequency of antibody responses and higher mean postvaccination anti-NA titers to the N1 and N2 of the A/H1N1 and A/H3N2 viruses in the vaccines than did the standard vaccine. Ensuring an increased antibody response to the NA antigen in inactivated influenza virus vaccines should increase the protection against influenza. An increased quantity of the NA antigen in the vaccine will ensure an increased response., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Vaccination is the most effective means for the prevention of influenza, including pandemic strains. An ideal pandemic influenza vaccine should provide effective protection with the fewest number of doses in the shortest amount of time, and among the greatest proportion of the population. The current manufacturing processes required for embryonated chicken-egg-based influenza vaccines are limited in their ability to respond to pandemic situations - these limitations include problems with surge capacity, the need for egg-adapted strains, the possibility of contamination, and the presence of trace egg protein. Several vaccine strategies to circumvent the deficiencies intrinsic to an egg-based influenza vaccine are in various phases of development. These include the use of cell-culture-based growth systems, concomitant use of adjuvants, whole virus vaccines, recombinant protein vaccines, plasmid DNA vaccines, virus-like particle vaccines, and universal flu vaccines.

A total of 600 healthy adults > or =65 years were randomized to receive 2 vaccinations 1 month apart of a subvirion avian influenza A/H5N1 vaccine containing 3.75, 7.5, 15, or 45microg of hemagglutinin (HA) with or without aluminum hydroxide (AlOH). All formulations were safe. Groups given the vaccine with AlOH had more injection site discomfort. Dose-related increases in antibody responses were noted after the second vaccination. Antibody responses to the vaccine were not enhanced by AlOH at any HA dose level. A microneutralization titer > or =40 was observed in 36% and 40% of subjects who received 45microg of HA with or without AlOH, respectively.

To improve immune responses to influenza vaccine, a trivalent inactivated vaccine containing 60 microg of the HA of each component (A/H3N2, A/H1N1, B) was compared to a licensed vaccine containing 15 microg of the HA of each. More local and systemic reactions were reported by subjects given the high dosage but only local pain and myalgias were significantly increased. The high dosage vaccine induced a higher frequency of serum antibody increases (> or =4-fold) in both hemagglutination-inhibiting (HAI) and neutralization tests for all three vaccine viruses in the total group as well as subjects vaccinated and those not vaccinated the previous year. Mean titers of antibody attained, the magnitude of antibody increases and the frequencies of persons with final HAI antibody titers > or =1:32, > or =1:64, and > or =1:128 were all greater for the high dosage group in both serologic tests, for all groups, and for all vaccine viruses. These increased immune responses should provide increased protection against influenza in the elderly.

Current seasonal influenza virus vaccines engender antibody-mediated protection that is hemagglutinin (HA) subtype specific and relatively short-lived. Coverage for other subtypes or even variants within a subtype could be improved from a better understanding of the factors that promote HA-specific antibody cross-reactivity. Current assays to evaluate cross-reactivity, such as the ELISA, require a separate test for each antigen and are neither high-throughput nor sample-sparing. To address this need, we produced an array of 283 purified HA proteins from influenza A virus subtypes H1 to H16 and H18 and influenza B virus. To evaluate performance, arrays were probed with sera from individuals before and after a booster dose of inactivated heterologous H5N1 vaccine and naturally infected cases at presentation and follow-up during the 2010 to 2011 influenza season, when H3N2 was prevalent. The response to the H5 vaccine boost was IgG only and confined to H5 variants. The response to natural H3N2 infection consisted of IgG and IgA and was reactive with all H3 variants displayed, as well as against other group 2 HA subtypes. In both groups, responses to HA1 proteins were subtype specific. In contrast, baseline signals were higher, and responses broader, against full-length HA proteins (HA1+HA2) compared to HA1 alone. We propose that these elevated baseline signals and breadth come from the recognition of conserved epitopes in the stalk domain by cross-reactive antibodies accumulated from previous exposure(s) to seasonal influenza virus. This array is a valuable high-throughput alternative to the ELISA for monitoring specificity and cross-reactivity of HA antibodies and has many applications in vaccine development.IMPORTANCE Seasonal influenza is a serious public health problem because the viral infection spreads easily from person to person and because of antigenic drift in neutralizing epitopes. Influenza vaccination is the most effective way to prevent the disease, although challenging because of the constant evolution of influenza virus subtypes. Our high-throughput protein microarrays allow for interrogation of subunit-specific IgG and IgA responses to 283 different HA proteins comprised of HA1 and HA2 domains as well as full-length HA proteins. This provides a tool that allows for novel insights into the response to exposure to influenza virus antigens. Data generated with our technology will enhance our understanding of the factors that improve the strength, breadth, and durability of vaccine-mediated immune responses and develop more effective vaccines.

Invasive Haemophilus influenzae type b (Hib) disease is a serious bacterial infection that disproportionally affects American Indian and Alaska Native (AI/AN) populations. Hib vaccination with a monovalent Hib conjugate vaccine consisting of Hib capsular polysaccharide (polyribosylribitol phosphate [PRP]) conjugated to outer membrane protein complex of Neisseria meningitidis serogroup B, PRP-OMP (PedvaxHIB, Merck and Co., Inc.) has historically been preferred for AI/AN infants, who are at increased risk for invasive Hib disease, because it provides substantial protection after the first dose. On June 26, 2024, CDC's Advisory Committee on Immunization Practices (ACIP) recommended that a hexavalent, combined diphtheria and tetanus toxoids and acellular pertussis (DTaP), inactivated poliovirus (IPV), Hib conjugate, and hepatitis B (HepB) vaccine, DTaP-IPV-Hib-HepB (Vaxelis, MSP Vaccine Company) should be included with monovalent PRP-OMP in the preferential recommendation for AI/AN infants because of the PRP-OMP Hib component. A primary Hib vaccination series consisting of either 1) monovalent PRP-OMP (2-dose series at ages 2 and 4 months) or 2) DTaP-IPV-Hib-HepB (3-dose series at ages 2, 4, and 6 months) is preferred for AI/AN infants. DTaP-IPV-Hib-HepB is only indicated for use in infants at ages 2, 4, and 6 months and should not be used for the booster doses of Hib, DTaP, or IPV vaccines. For the booster dose of Hib vaccine, no vaccine formulation is preferred for AI/AN children; any Hib vaccine (except DTaP-IPV-Hib-HepB) should be used. This report summarizes evidence considered for these recommendations and provides clinical guidance for the use of Hib-containing vaccines among AI/AN infants and children. [ABSTRACT FROM AUTHOR]

Current seasonal and pre-pandemic influenza vaccines induce short-lived predominantly strain-specific and limited heterosubtypic responses. To better understand how vaccine adjuvants AS03 and MF59 may provide improved antibody responses to vaccination, we interrogated serum from subjects who received 2 doses of inactivated monovalent influenza A/Indonesia/05/2005 vaccine with or without AS03 or MF59 using hemagglutinin (HA) microarrays (NCT01317758 and NCT01317745). The arrays were designed to reflect both full-length and globular head HA derived from 17 influenza A subtypes (H1 to H16 and H18) and influenza B strains. We observed significantly increased strain-specific and broad homo- and heterosubtypic antibody responses with both AS03 and MF59 adjuvanted vaccination with AS03 achieving a higher titer and breadth of IgG responses relative to MF59. The adjuvanted vaccine was also associated with the elicitation of stalk-directed antibody. We established good correlation of the array antibody responses to H5 antigens with standard HA inhibition and microneutralization titers. [ABSTRACT FROM AUTHOR]

Background Influenza vaccination is uncommon in low-resource settings. We evaluated aspects of operational feasibility of influenza vaccination programs targeting risk groups in the World Health Organization (WHO) African (AFR) and South-East Asian (SEAR) Regions. Methods We estimated routine immunization and influenza vaccination campaign doses, doses per vaccinator, and cold storage requirements for 1 simulated country in each region using evidence-based population distribution, vaccination schedule, and vaccine volumes. Influenza vaccination targeted persons <5 years, pregnant women, persons with chronic diseases, persons ≥65 years, and healthcare workers (HCW). For the AFR country, we compared vaccine volumes to actual storage capacities. Results Targeting HCW had a small operational impact, and subsequent findings exclude this group. During 3-month influenza vaccination campaigns, monthly doses delivered in the AFR country increased from 15.0% for ≥65 years to 93.1% for <5 years and in the SEAR country from 19.6% for pregnant women to 145.0% for persons with chronic diseases. National-level cold storage capacity requirements increased in the AFR country from 4.1% for ≥65 years to 20.3% for <5 years and in the SEAR country from 3.9% for pregnant women to 28.8% for persons with chronic diseases. Subnational-level cold storage capacity requirements increased in the AFR country from 5.9% for ≥65 years to 36.8% for <5 years and the SEAR country from 17.6% for pregnant women to 56.0% for persons with chronic diseases. Conclusions Influenza vaccination of most risk groups will require substantial increases in doses, doses per vaccinator, and cold storage capacity in countries where infrastructure and resources are limited. [ABSTRACT FROM AUTHOR]

There is a pressing need to develop alternatives to annual influenza vaccines and antiviral agents licensed for mitigating influenza infection. Previous studies reported that acute lung injury caused by chemical or microbial insults is secondary to the generation of host-derived, oxidized phospholipid that potently stimulates Toll-like receptor 4 (TLR4)-dependent inflammation. Subsequently, we reported that Tlr4−/− mice are highly refractory to influenza-induced lethality, and proposed that therapeutic antagonism of TLR4 signalling would protect against influenza-induced acute lung injury. Here we report that therapeutic administration of Eritoran (also known as E5564)-a potent, well-tolerated, synthetic TLR4 antagonist-blocks influenza-induced lethality in mice, as well as lung pathology, clinical symptoms, cytokine and oxidized phospholipid expression, and decreases viral titres. CD14 and TLR2 are also required for Eritoran-mediated protection, and CD14 directly binds Eritoran and inhibits ligand binding to MD2. Thus, Eritoran blockade of TLR signalling represents a novel therapeutic approach for inflammation associated with influenza, and possibly other infections. [ABSTRACT FROM AUTHOR]