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Rodman Tarigan Girsang,1 Eddy Fadlyana,1 Kusnandi Rusmil,1 Muhammad Gilang Dwi Putra,1 Rona Kania Utami,1 Alvira Dwilestarie Putri,1 Hadyana Sukandar2 1Child Health Department, Faculty of Medicine Universitas Padjadjaran/Hasan Sadikin Hospital, Bandung City, West Java, Indonesia; 2Public Health Department, Faculty of Medicine Universitas Padjadjaran, Bandung City, West Java, IndonesiaCorrespondence: Eddy Fadlyana, Email eddy.fadlyana@unpad.ac.idAbstract: Nearly 3 years after the emergence of COVID-19, it remains one of the world’s problems. COVID-19 vaccination is a priority programme for reducing death and severe symptoms. The primary recombinant novel coronavirus ZF2001 vaccine has gone through Phase III clinical trials and demonstrates efficacy against the highly critical COVID-19 globally and in Indonesia (87.6% and 76.0%, respectively). This study aimed to assess immune persistence after three doses of ZF2001. The study monitored and followed up 400 participants 14 days and 6 months after the third dose and investigated immune persistence 6 months after the phase III vaccination (ZF2001). This study was conducted at recruitment locations in Bandung. Participants were divided into the vaccine and placebo groups and entered into the immunogenicity group. The immune persistence of the vaccine was assessed by measuring geometric mean titres (GMT), neutralising antibodies and seropositivity of IgG anti-S-receptor-binding domain (RBD) after 14 days and 6 months. The seropositive antibody rates were nearly the same between 14 days and 6 months. After 6 months, the GMT, seropositivity of IgG anti-S-RBD and neutralising antibodies in the vaccine group decreased significantly, from 6447.63 to 1514.61 with a P-value of 0.001. A booster was considered important after 6 months.Keywords: recombinant novel coronavirus, ZF2001, vaccine, COVID-19

The factors affecting the antibody responses to the ZF2001 vaccine remain unknown. To address this, we conducted a cross-sectional serological study in the real world. Adults with no prior SARS-CoV-2 infection history and received three doses of ZF2001 vaccine were invited to our study in the early stages of the COVID-19 epidemic in Chongqing between 7 April 2021 and 17 November 2021. A questionnaire survey was conducted to obtain demographic characteristics, health information, and the frequency of lifestyles at the time of enrollment. A total of 266 eligible subjects aged 18 to 86 years, with a median age of 56.00 (IQR: 34–66) participated. 68.80% of them were female. Hypertension (13.16%) and diabetes (6.02%) were common comorbidities. Serum samples were collected at one month after the third dose of ZF2001 vaccination, and serological testing was conducted using the Pseudovirus-Based Neutralization Assay. The chi-square test was employed to compare seropositivity rates, and the Mann-Whitney U test or the Kruskal–Wallis test was used to analyze the neutralizing antibodies level in stratified groups. Subsequently, univariate and multivariate linear regression analyses were conducted to identify the influencing factors. We observed that seropositivity rates was 76.32%, with 95% confidence interval (95%CI) 70.85%–81.03%, and geometric mean titer (GMT) was 120.26, with 95%CI 100.38–144.08. Age, diabetes, and frequently of alcohol were negative associations with antibody response (β = -0.2021, 95% CI: −0.2507 to −0.1535, β = -0.2873, 95% CI: −0.5590 to −0.0155, β = -0.2082, 95% CI: −0.3419 to-0.0746, P < 0.0001, P = 0.0384, P = 0.0024). Conversely, the -interval between 1 and 2 dose and frequently of tea were positive associations with antibody response (β = 0.1369, 95% CI: 0.0463 to 0.2275, β = 0.0830, 95% CI: 0.0106 to 0.1554, P = 0.0032, P = 0.0247). Overall, the ZF2001 vaccine-induced antibody response was influenced by a multifactor that may provide a reference for the development of personalized antigen vaccines and vaccination strategies in the future.

The ZF2001 vaccine has demonstrated high efficacy in preventing coronavirus disease 2019 (COVID-19). However, the clinical characteristics of breakthrough infections in vaccinated individuals and the risk factors for adverse outcomes in COVID-19 patients remain unclear. We conducted a retrospective single-center cohort study at Xiangya Hospital of Central South University, including 210 fully vaccinated COVID-19 inpatients from December 5, 2022, to January 31, 2023. Data on clinical characteristics, laboratory findings, disease severity, treatment, and prognosis were collected and analyzed. Our findings revealed that COVID-19 inpatients still experienced common symptoms at the onset of illness, but most laboratory findings were within the normal range, except for white blood cell count (WBC), lymphocyte count, and lactate dehydrogenase (LDH) levels. Following standard treatment, 95.7% of patients were discharged from the hospital. We identified seven variables significantly associated with a higher risk of adverse outcomes, including age over 65, elevated WBC count, reduced lymphocyte count, higher levels of blood urea nitrogen (BUN), LDH, troponin, D-dimer, and procalcitonin. This study supports the substantial clinical benefits of the ZF2001 vaccine for COVID-19 patients. Additionally, age over 65, elevated WBC count, reduced lymphocyte count, and higher blood levels of BUN, LDH, D-dimer, and procalcitonin may be used as predictive factors for disease progression in fully vaccinated COVID-19 inpatients.

ABSTRACTThe SARS-CoV-2 Omicron variants of concern (VOCs) showed severe resistance to the early-approved COVID-19 vaccines-induced immune responses. The breakthrough infections by the Omicron VOCs are currently the major challenge for pandemic control. Therefore, booster vaccination is crucial to enhance immune responses and protective efficacy. Previously, we developed a protein subunit COVID-19 vaccine ZF2001, based on the immunogen of receptor-binding domain (RBD) homodimer, which was approved in China and other countries. To adapt SARS-CoV-2 variants, we further developed chimeric Delta-Omicron BA.1 RBD-dimer immunogen which induced broad immune responses against SARS-CoV-2 variants. In this study, we tested the boosting effect of this chimeric RBD-dimer vaccine in mice after priming with two doses of inactivated vaccines, compared with a booster of inactivated vaccine or ZF2001. The results demonstrated that boosting with bivalent Delta-Omicron BA.1 vaccine greatly promoted the neutralizing activity of the sera to all tested SARS-CoV-2 variants. Therefore, the Delta-Omicron chimeric RBD-dimer vaccine is a feasible booster for those with prior vaccination of COVID-19 inactivated vaccines.

The coronavirus disease 2019 (COVID‐19) pandemic posed great impacts on public health. To fight against the pandemic, robust immune responses induced by vaccination are indispensable. Previously, we developed a subunit vaccine adjuvanted by aluminum hydroxide, ZF2001, based on the dimeric tandem‐repeat RBD immunogen, which has been approved for clinical use. This dimeric RBD design was also explored as an mRNA vaccine. Both showed potent immunogenicity. In this study, a DNA vaccine candidate encoding RBD‐dimer was designed. The humoral and cellular immune responses induced by homologous and heterologous prime‐boost approaches with DNA‐RBD‐dimer and ZF2001 were assessed in mice. Protection efficacy was studied by the SARS‐CoV‐2 challenge. We found that the DNA‐RBD‐dimer vaccine was robustly immunogenic. Priming with DNA‐RBD‐dimer followed by ZF2001 boosting induced higher levels of neutralizing antibodies than homologous vaccination with either DNA‐RBD‐dimer or ZF2001, elicited polyfunctional cellular immunity with a TH1‐biased polarization, and efficiently protected mice against SARS‐CoV‐2 infection in the lung. This study demonstrated the robust and protective immune responses induced by the DNA‐RBD‐dimer candidate and provided a heterologous prime‐boost approach with DNA‐RBD‐dimer and ZF2001. [ABSTRACT FROM AUTHOR]

Safe, efficacious, and deployable vaccines are urgently needed to control COVID-19 in the large-scale vaccination campaigns. We report here the preclinical studies of an approved protein subunit vaccine against COVID-19, ZF2001, which contains tandem-repeat dimeric receptor-binding domain (RBD) protein with alum-based adjuvant. We assessed vaccine immunogenicity and efficacy in both mice and non-human primates (NHPs). ZF2001 induced high levels of RBD-binding and SARS-CoV-2 neutralizing antibody in both mice and non-human primates, and elicited balanced TH1/TH2 cellular responses in NHPs. Two doses of ZF2001 protected Ad-hACE2-transduced mice against SARS-CoV-2 infection, as detected by reduced viral RNA and relieved lung injuries. In NHPs, vaccination of either 25 μg or 50 μg ZF2001 prevented infection with SARS-CoV-2 in lung, trachea, and bronchi, with milder lung lesions. No evidence of disease enhancement was observed in both animal models. ZF2001 has been approved for emergency use in China, Uzbekistan, Indonesia, and Columbia. The high safety, immunogenicity, and protection efficacy in both mice and NHPs found in this preclinical study was consistent with the results in human clinical trials.

Objectives. Since the outbreak of SARS-CoV-2 in late 2019, nearly 12.2 billion doses of the COVID-19 vaccine have been administered worldwide; however, the humoral immune responses induced by different types of vaccines are yet to be fully validated. Methods. We analyzed antibody levels in 100 serum samples after vaccination with different types of COVID-19 vaccines and their reactivity against the RBD antigen of Delta and Omicron variants using a bead-based microarray. Results. Elevated levels of anti-wild-type (WT)-RBD IgG and anti-WT-NP IgG were detected in participants who received two doses of the inactivated vaccines (CoronaVac or BBIBP-CorV) and three doses of the recombinant spike protein vaccine (ZF2001), indicating that antibody responses to SARS-CoV-2 were generated regardless of the vaccine administered. We found highly correlated levels of serum anti-RBD IgG and anti-NP IgG (r = 0.432, p < 0.001). We observed that the antibodies produced in vivo after COVID-19 vaccination still reacted with variants of SARS-CoV-2 (p < 0.0001). Conclusions. Our results show that high levels of specific antibodies can be produced after completion of COVID-19 vaccination (two doses of the inactivated vaccines or three doses of ZF2001), with some degree of cross-reactivity to the RBD antigen of Delta and Omicron variants, and provide an accessible and practical experimental method for post-vaccination antibody detection. [ABSTRACT FROM AUTHOR]

Abstract To investigate the protective efficacy and mechanism of ZF2001 (a protein subunit vaccine with conditional approval in China) to SARS-CoV-2 Delta variant-induced severe pneumonia, the lethal challenge model of K18-hACE2 transgenic mice was used in this study. An inactivated-virus vaccine at the research and development stage (abbreviated as RDINA) was compared to ZF2001. We found that ZF2001 and RDINA could provide the protective effect against Delta variant-induced severe cases, as measured by the improved survival rates, the reduced virus loads, the alleviated lung histopathology and the high neutralizing antibody geomean titers, compared to aluminum adjuvant group. To prevent and control Omicron or other variant epidemics, further improvements in vaccine design and compatibilities with the novel adjuvant are required to achieve better immunogenicity.

Background and aimsAlthough COVID-19 vaccination is recommended for the patients with chronic liver disease, the clinical outcomes of COVID-19 vaccinated in patients with chronic hepatitis B (CHB) has not been well characterized. The study aimed to explore the safety and specific antibody responses following COVID-19 vaccination among CHB patients.MethodsPatients with CHB were included. All patients were vaccinated with two doses of inactivated vaccine (CoronaVac) or three doses of adjuvanted protein subunit vaccine (ZF2001). The adverse events were recorded and neutralizing antibody (NAb) were determined 14 days following the whole-course vaccination.ResultsA total of 200 patients with CHB were included. Specific NAb against SARS-CoV-2 were positive in 170 (84.6%) patients. The median (IQR) concentrations of NAb were 16.32 (8.44–34.10) AU/ml. Comparison of immune responses between CoronaVac and ZF2001 vaccines showed no significant differences in neither the concentrations of NAb nor the seropositive rates (84.4 vs. 85.7%). Moreover, we observed lower immunogenicity in older patients and in patients with cirrhosis or underlying comorbidities. The incidences of adverse events were 37 (18.5%) with the most common adverse event as injection side pain [25 (12.5%)], followed by fatigue [15 (7.5%)]. There were no differences in the frequencies of adverse between CoronaVac and ZF2001 (19.3% vs. 17.6%). Almost all of the adverse reactions were mild and self-resolved within a few days after vaccination. Severe adverse events were not observed.ConclusionsCOVID-19 vaccines, CoronaVac and ZF2001 had a favorable safety profile and induced efficient immune response in patients with CHB.

To investigate the protective efficacy and mechanism of ZF2001 (a protein subunit vaccine with conditional approval in China) to SARS-CoV-2 Delta variant-induced severe pneumonia, the lethal challenge model of K18-hACE2 transgenic mice was used in this study. An inactivated-virus vaccine at the research and development stage (abbreviated as RDINA) was compared to ZF2001. We found that ZF2001 and RDINA could provide the protective effect against Delta variant-induced severe cases, as measured by the improved survival rates, the reduced virus loads, the alleviated lung histopathology and the high neutralizing antibody geomean titers, compared to aluminum adjuvant group. To prevent and control Omicron or other variant epidemics, further improvements in vaccine design and compatibilities with the novel adjuvant are required to achieve better immunogenicity. [ABSTRACT FROM AUTHOR]

The factors affecting the antibody responses to the ZF2001 vaccine remain unknown. To address this, we conducted a cross-sectional serological study in the real world. Adults with no prior SARS-CoV-2 infection history and received three doses of ZF2001 vaccine were invited to our study in the early stages of the COVID-19 epidemic in Chongqing between 7 April 2021 and 17 November 2021. A questionnaire survey was conducted to obtain demographic characteristics, health information, and the frequency of lifestyles at the time of enrollment. A total of 266 eligible subjects aged 18 to 86 years, with a median age of 56.00 (IQR: 34-66) participated. 68.80% of them were female. Hypertension (13.16%) and diabetes (6.02%) were common comorbidities. Serum samples were collected at one month after the third dose of ZF2001 vaccination, and serological testing was conducted using the Pseudovirus-Based Neutralization Assay. The chi-square test was employed to compare seropositivity rates, and the Mann-Whitney U test or the Kruskal-Wallis test was used to analyze the neutralizing antibodies level in stratified groups. Subsequently, univariate and multivariate linear regression analyses were conducted to identify the influencing factors. We observed that seropositivity rates was 76.32%, with 95% confidence interval (95%CI) 70.85%-81.03%, and geometric mean titer (GMT) was 120.26, with 95%CI 100.38-144.08. Age, diabetes, and frequently of alcohol were negative associations with antibody response ( β = -0.2021, 95% CI: -0.2507 to -0.1535, β = -0.2873, 95% CI: -0.5590 to -0.0155, β = -0.2082, 95% CI: -0.3419 to-0.0746, P < 0.0001, P  = 0.0384, P  = 0.0024). Conversely, the -interval between 1 and 2 dose and frequently of tea were positive associations with antibody response ( β  = 0.1369, 95% CI: 0.0463 to 0.2275, β  = 0.0830, 95% CI: 0.0106 to 0.1554, P  = 0.0032, P  = 0.0247). Overall, the ZF2001 vaccine-induced antibody response was influenced by a multifactor that may provide a reference for the development of personalized antigen vaccines and vaccination strategies in the future.

The ZF2001 vaccine has demonstrated high efficacy in preventing coronavirus disease 2019 (COVID-19). However, the clinical characteristics of breakthrough infections in vaccinated individuals and the risk factors for adverse outcomes in COVID-19 patients remain unclear. We conducted a retrospective single-center cohort study at Xiangya Hospital of Central South University, including 210 fully vaccinated COVID-19 inpatients from December 5, 2022, to January 31, 2023. Data on clinical characteristics, laboratory findings, disease severity, treatment, and prognosis were collected and analyzed. Our findings revealed that COVID-19 inpatients still experienced common symptoms at the onset of illness, but most laboratory findings were within the normal range, except for white blood cell count (WBC), lymphocyte count, and lactate dehydrogenase (LDH) levels. Following standard treatment, 95.7% of patients were discharged from the hospital. We identified seven variables significantly associated with a higher risk of adverse outcomes, including age over 65, elevated WBC count, reduced lymphocyte count, higher levels of blood urea nitrogen (BUN), LDH, troponin, D-dimer, and procalcitonin. This study supports the substantial clinical benefits of the ZF2001 vaccine for COVID-19 patients. Additionally, age over 65, elevated WBC count, reduced lymphocyte count, and higher blood levels of BUN, LDH, D-dimer, and procalcitonin may be used as predictive factors for disease progression in fully vaccinated COVID-19 inpatients.

Objectives. Since the outbreak of SARS-CoV-2 in late 2019, nearly 12.2 billion doses of the COVID-19 vaccine have been administered worldwide; however, the humoral immune responses induced by different types of vaccines are yet to be fully validated. Methods. We analyzed antibody levels in 100 serum samples after vaccination with different types of COVID-19 vaccines and their reactivity against the RBD antigen of Delta and Omicron variants using a bead-based microarray. Results. Elevated levels of anti-wild-type (WT)-RBD IgG and anti-WT-NP IgG were detected in participants who received two doses of the inactivated vaccines (CoronaVac or BBIBP-CorV) and three doses of the recombinant spike protein vaccine (ZF2001), indicating that antibody responses to SARS-CoV-2 were generated regardless of the vaccine administered. We found highly correlated levels of serum anti-RBD IgG and anti-NP IgG (r = 0.432, p < 0.001). We observed that the antibodies produced in vivo after COVID-19 vaccination still reacted with variants of SARS-CoV-2 (p < 0.0001). Conclusions. Our results show that high levels of specific antibodies can be produced after completion of COVID-19 vaccination (two doses of the inactivated vaccines or three doses of ZF2001), with some degree of cross-reactivity to the RBD antigen of Delta and Omicron variants, and provide an accessible and practical experimental method for post-vaccination antibody detection.

The SARS-CoV-2 spike protein receptor-binding domain (RBD), which is a key target for the development of SARS-CoV-2 neutralizing antibodies and vaccines, mediates the binding of the host receptor angiotensin-converting enzyme 2 (ACE2). However, the high heterogeneity of RBD glycoforms may lead to an incomplete neutralization effect and impact the immunogenicity of RBD-based vaccines (Ye et al., 2021). Here, our data suggested that the glycosylation significantly affected the humoral immunogenicity and immunoreactivity of the RBD-dimer-based Covid-19 vaccine (ZF2001) (Yang et al., 2021). Several deglycosylated types of ZF2001 (with sialic acid removed (ZF2001-ΔSA), sialic acid & O-glycans removed (ZF2001-ΔSA&O), N-glycans removed (ZF2001-ΔN), N- & O-glycans removed (ZF2001-ΔN&O)) were obtained by treatment with glycosidases. The binding affinity between deglycosylated types of ZF2001 and ACE2 was slightly weakened and that between deglycosylated types of ZF2001 and several monoclonal antibodies (mAbs) were also changed compared with ZF2001. The results of pseudovirus neutralization assay and binding affinity assay of all ZF2001 types revealed that the antigens with complex glycosylation had better humoral immunogenicity and immunoreactivity. Molecular dynamics simulation indicated that the more complex glycosylation of RBD corresponded to more hydrogen bonds formed between helper T-cell epitopes of RBD and major histocompatibility complex II (MHC-II). In summary, these results demonstrated that the glycosylation of RBD affects antigen presentation, humoral immunogenicity and immunoreactivity, which may be an important consideration for vaccine design and production technology. [ABSTRACT FROM AUTHOR]

Background and Aims: Although COVID-19 vaccination is recommended for the patients with chronic liver disease, the clinical outcomes of COVID-19 vaccinated in patients with chronic hepatitis B (CHB) has not been well characterized. The study aimed to explore the safety and specific antibody responses following COVID-19 vaccination among CHB patients., Methods: Patients with CHB were included. All patients were vaccinated with two doses of inactivated vaccine (CoronaVac) or three doses of adjuvanted protein subunit vaccine (ZF2001). The adverse events were recorded and neutralizing antibody (NAb) were determined 14 days following the whole-course vaccination., Results: A total of 200 patients with CHB were included. Specific NAb against SARS-CoV-2 were positive in 170 (84.6%) patients. The median (IQR) concentrations of NAb were 16.32 (8.44-34.10) AU/ml. Comparison of immune responses between CoronaVac and ZF2001 vaccines showed no significant differences in neither the concentrations of NAb nor the seropositive rates (84.4 vs. 85.7%). Moreover, we observed lower immunogenicity in older patients and in patients with cirrhosis or underlying comorbidities. The incidences of adverse events were 37 (18.5%) with the most common adverse event as injection side pain [25 (12.5%)], followed by fatigue [15 (7.5%)]. There were no differences in the frequencies of adverse between CoronaVac and ZF2001 (19.3% vs. 17.6%). Almost all of the adverse reactions were mild and self-resolved within a few days after vaccination. Severe adverse events were not observed., Conclusions: COVID-19 vaccines, CoronaVac and ZF2001 had a favorable safety profile and induced efficient immune response in patients with CHB., Competing Interests: The 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 © 2023 Wu, Wang, Feng, Liu, Fan, Ran, Wang and Wang.)

Safe, efficacious, and deployable vaccines are urgently needed to control COVID-19 in the large-scale vaccination campaigns. We report here the preclinical studies of an approved protein subunit vaccine against COVID-19, ZF2001, which contains tandem-repeat dimeric receptor-binding domain (RBD) protein with alum-based adjuvant. We assessed vaccine immunogenicity and efficacy in both mice and non-human primates (NHPs). ZF2001 induced high levels of RBD-binding and SARS-CoV-2 neutralizing antibody in both mice and non-human primates, and elicited balanced T H 1/T H 2 cellular responses in NHPs. Two doses of ZF2001 protected Ad-hACE2-transduced mice against SARS-CoV-2 infection, as detected by reduced viral RNA and relieved lung injuries. In NHPs, vaccination of either 25 μg or 50 μg ZF2001 prevented infection with SARS-CoV-2 in lung, trachea, and bronchi, with milder lung lesions. No evidence of disease enhancement was observed in both animal models. ZF2001 has been approved for emergency use in China, Uzbekistan, Indonesia, and Columbia. The high safety, immunogenicity, and protection efficacy in both mice and NHPs found in this preclinical study was consistent with the results in human clinical trials.