Safety and immunogenicity of inactivated COVID-19 vaccine in health care workers

High SARS-CoV-2 infection rate in children unvaccinated with COVID-19 vaccine in Changzhou, China, shortly after lifting zero-COVID-19 policy in December 2022

BACKGROUND

China experienced an overwhelming COVID-19 pandemic from middle December 2022 to middle January 2023 after lifting the zero-COVID-19 policy on December 7, 2022. However, the infection rate was less studied. We aimed to investigate the SARS-CoV-2 infection rate in children shortly after discontinuation of the zero-COVID-19 policy.

METHODS

From February 20 to April 10, 2023, we included 393 children aged 8 months to less than 3 years who did not receive COVID-19 vaccination and 114 children aged 3 to 6 years who received inactivated COVID-19 vaccines based on the convenience sampling in this cross-sectional study. IgG and IgM antibodies against nucleocapsid (N) and subunit 1 of spike (S1) of SARS-CoV-2 (anti-N/S1) were measured with commercial kits (Shenzhen YHLO Biotech, China).

RESULTS

Of the 393 unvaccinated children (1.5 ± 0.6 years; 52.2% boys), 369 (93.9%) were anti-N/S1 IgG positive. Of the 114 vaccinated children (5.3 ± 0.9 years; 48.2% boys), 112 (98.2%) were anti-N/S1 IgG positive. None of the unvaccinated or vaccinated children was anti-N/S1 IgM positive. The median IgG antibody titers in vaccinated children (344.91 AU/mL) were significantly higher than that in unvaccinated children (42.80 AU/mL) (P < 0.0001). The positive rates and titers of anti-N/S1 IgG had no significant difference between boys and girls respectively.

CONCLUSION

Vast majority of children were infected with SARS-CoV-2 shortly after ending zero-COVID-19 policy in China. Whether these unvaccinated infected children should receive COVID-19 vaccine merits further investigation.

How has research on the effectiveness and safety of COVID-19 vaccination been evaluated: a scope review with emphasis on CoronaVac

Introduction

The control of the COVID-19 epidemic has been focused on the development of vaccines against SARS-CoV-2. All developed vaccines have reported safety and efficacy results in preventing infection and its consequences, although the quality of evidence varies depending on the vaccine considered. Different methodological designs have been used for their evaluation, which can influence our understanding of the effects of these interventions. CoronaVac is an inactivated vaccine, and it has been assessed in various studies, including clinical trials and observational studies. Given these differences, our objective was to explore the published information to answer the question: how has the efficacy/effectiveness and safety of CoronaVac been evaluated in different studies? This is to identify potential gaps and challenges to be addressed in understanding its effect.

Methods

A scoping review was carried out following the methodology proposed by the Joanna Briggs Institute, which included studies carried out in humans as of 2020, corresponding to systematic reviews, clinical trials, analytical or descriptive observational studies, in which the effectiveness and/or safety of vaccines for COVID19 were evaluated or described. There were no age restrictions for the study participants.

Results

The efficacy/effectiveness and safety of this vaccine was assessed through 113 studies. Nineteen corresponded to experimental studies, 7 of Phase II, 5 of Phase IV, and 4 were clinical trials with random assignment. Although some clinical trials with random assignment have been carried out, these have limitations in terms of feasibility, follow-up times, and with this, the possibility of evaluating safety outcomes that occur with low frequencies. Not all studies have used homogeneous methods of analysis. Both the prevention of infection, and the prevention of outcomes such as hospitalization or death, have been valued through similar outcomes, but some through multivariate analysis of dependencies, and others through analysis that try to infer causally through different control methods of confounding.

Conclusion

Published information on the evaluation of the efficacy/effectiveness and safety of the CoronaVac is abundant. However, there are differences in terms of vaccine application schedules, population definition, outcomes evaluated, follow-up times, and safety assessment, as well as non-standardization in the reporting of results, which may hinder the generalizability of the findings. It is important to generate meetings and consensus strategies for the methods and reporting of this type of studies, which will allow to reduce the heterogeneity in their presentation and a better understanding of the effect of these vaccines.

Unveiling the micronutrient-immunity puzzle in inactivated COVID-19 vaccination: A comprehensive analysis of circulating micronutrient levels and humoral responses in healthy adults

While micronutrients are crucial for immune function, their impact on humoral responses to inactivated COVID-19 vaccination remains unclear. We investigated the associations between seven key micronutrients and antibody responses in 44 healthy adults with two doses of an inactivated COVID-19 vaccine. Blood samples were collected pre-vaccination and 28 days post-booster. We measured circulating minerals (iron, zinc, copper, and selenium) and vitamins (A, D, and E) concentrations alongside antibody responses and assessed their associations using linear regression analyses. Our analysis revealed inverse associations between blood iron and zinc concentrations and anti-SARS-CoV-2 IgM antibody binding affinity (AUC for iron: β = -258.21, p < 0.0001; zinc: β = -17.25, p = 0.0004). Notably, antibody quality presented complex relationships. Blood selenium was positively associated (β = 18.61, p = 0.0030), while copper/selenium ratio was inversely associated (β = -1.36, p = 0.0055) with the neutralizing ability against SARS-CoV-2 virus at a 1:10 plasma dilution. There was no significant association between circulating micronutrient concentrations and anti-SARS-CoV-2 IgG binding affinity. These findings suggest that circulating iron, zinc, and selenium concentrations and copper/selenium ratio, may serve as potential biomarkers for both quantity (binding affinity) and quality (neutralization) of humoral responses after inactivated COVID-19 vaccination. Furthermore, they hint at the potential of pre-vaccination dietary interventions, such as selenium supplementation, to improve vaccine efficacy. However, larger, diverse studies are needed to validate these findings. This research advances the understanding of the impact of micronutrients on vaccine response, offering the potential for personalized vaccination strategies.

Durability of the Effectiveness of Heterologous COVID-19 Vaccine Regimens in Thailand: Retrospective Cohort Study Using National Registration Data

BACKGROUND

The durability of heterologous COVID-19 vaccine effectiveness (VE) has been primarily studied in high-income countries, while evaluation of heterologous vaccine policies in low- and middle-income countries remains limited.

OBJECTIVE

We aimed to evaluate the duration during which the VE of heterologous COVID-19 vaccine regimens in mitigating serious outcomes, specifically severe COVID-19 and death following hospitalization with COVID-19, remains over 50%.

METHODS

We formed a dynamic cohort by linking records of Thai citizens aged ≥18 years from citizen vital, COVID-19 vaccine, and COVID-19 cases registry databases between May 2021 and July 2022. Encrypted citizen identification numbers were used to merge the data between the databases. This study focuses on 8 common heterologous vaccine sequences: CoronaVac/ChAdOx1, ChAdOx1/BNT162b2, CoronaVac/CoronaVac/ChAdOx1, CoronaVac/ChAdOx1/ChAdOx1, CoronaVac/ChAdOx1/BNT162b2, BBIBP-CorV/BBIBP-CorV/BNT162b2, ChAdOx1/ChAdOx1/BNT162b2, and ChAdOx1/ChAdOx1/mRNA-1273. Nonimmunized individuals were considered for comparisons. The cohort was stratified according to the vaccination status, age, sex, province location, month of vaccination, and outcome. Data analysis employed logistic regression to determine the VE, accounting for potential confounders and durability over time, with data observed over a follow-up period of 7 months.

RESULTS

This study includes 52,580,841 individuals, with approximately 17,907,215 and 17,190,975 receiving 2- and 3-dose common heterologous vaccines (not mutually exclusive), respectively. The 2-dose heterologous vaccinations offered approximately 50% VE against severe COVID-19 and death following hospitalization with COVID-19 for 2 months; however, the protection significantly declined over time. The 3-dose heterologous vaccinations sustained over 50% VE against both outcomes for at least 8 months, as determined by logistic regression with durability time-interaction modeling. The vaccine sequence consisting of CoronaVac/CoronaVac/ChAdOx1 demonstrated >80% VE against both outcomes, with no evidence of VE waning. The final monthly measured VE of CoronaVac/CoronaVac/ChAdOx1 against severe COVID-19 and death following hospitalization at 7 months after the last dose was 82% (95% CI 80.3%-84%) and 86.3% (95% CI 83.6%-84%), respectively.

CONCLUSIONS

In Thailand, within a 7-month observation period, the 2-dose regimens could not maintain a 50% VE against severe and fatal COVID-19 for over 2 months, but all of the 3-dose regimens did. The CoronaVac/CoronaVac/ChAdOx1 regimen showed the best protective effect against severe and fatal COVID-19. The estimated durability of 50% VE for at least 8 months across all 3-dose heterologous COVID-19 vaccine regimens supports the adoption of heterologous prime-boost vaccination strategies, with a primary series of inactivated virus vaccine and boosting with either a viral vector or an mRNA vaccine, to prevent similar pandemics in low- and middle-income countries.

Safety profile of inactivated COVID-19 in healthy adults aged ≥ 18 years: A passive surveillance in Indonesia

Coronavirus Disease 2019 (COVID-19) vaccination in Indonesia has shown effectiveness in reducing the morbidity and mortality of Covid-19. The study aims to evaluate the incidence rate and severity of Adverse Events Following Immunization (AEFI) of inactivated SARS-CoV-2 vaccine during the first quarter of 2021 until the second quarter of 2022 in Indonesia. More than two hundred million Sinovac/CoronaVac were given from January 13th, 2021, until June 30th, 2022. Data for this study were collected manually and electronically from the national vaccine safety website managed by the National Committee (NC) of AEFI Indonesia and the Ministry of Health Indonesia. The total number of injections observed in the study was 264,311,992 doses consisting of 142,449,795 (first dose), 121,613,324 (second dose), and 248,873 (booster dose). Of the injections given, 301 subjects with Serious AEFIs (SAE) and 10.261 subjects with non-serious AEFIs (AE) reported, with a majority of SAE and AEs found in the first dose. Most of the SAEs were classified as coincidental events by the NC AEFI (IR 0.8/1 million doses on first dose injection; 0.31 on second dose injection). ISRR (immunization stress-related response) is in the second rank of SAEs reported (0.59 IR/1 million doses on the first dose; 0.14 on the second dose). The incidence rate of SAEs and AEs, both in the variable of age, sex, and symptoms per 1 million dose injections in Indonesia, was very rare according to WHO guidelines. Most SAEs were classified as coincidences or unrelated to the vaccine. The result showed that the Sinovac/CoronaVac in Indonesia is safe.

Safety profile of inactivated COVID-19 vaccine in indonesian adults

Background

Vaccines are urgently needed to handle the morbidity and mortality of the COVID-19 pandemic in Indonesia. The inactivated vaccine is widely used in Indonesia's national immunization program due to its eligibility of stock, easier to transport, and considered to be more established than newer platforms. In this study, we aimed to evaluate the safety profile of the inactivated vaccine and analyze the safety profile between adults and the elderly.

Methods

A prospective analytical study was conducted to evaluate the safety profile of inactivated COVID-19 vaccine among healthy adults aged ≥ 18 years from September 2nd to December 28th, 2021, at ten primary health centers from 5 districts in Jakarta, Indonesia. The participants were instructed to record the symptoms after inactivated COVID-19 vaccine injection in the diary card for 28 days. Chi-square tests were carried out to analyze the relationship between the adverse event following immunization (AEFI) in adults and elderly groups.

Results

Four of 1113 participants were not included in this study due to the lack of follow-up. Out of 1109 participants, there were 1044 adults (18-59 years) and 65 elderly (>59 years). There were no serious AEFI cases reported. Most AEFI cases were mild to moderate and resolved after several days of injection. Local pain, myalgia and fatigue were the most frequent adverse events reported. We found that there was no correlation between the adults and elderly age group with the incidence of AEFI (p = 0.924) for local reactions (p = 0.181) and most of the systemic reactions (p = 0.629). However, there is an increased risk of fever in the elderly group compared to the adult group (OR 4.046, 95 % CI 1.794-9.124, p = 0.003) following immunization.

Conclusions

Our study demonstrated that the inactivated COVID-19 vaccine is safe, considering that all symptoms experienced were mild to moderate and resolved entirely.

Safety of Inactivated SARS-CoV-2 Vaccines Among Adults with Experience of Allergies to Food or Medicines

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), commonly known as COVID-19, poses significant risk to human health worldwide. The primary strategy for controlling the disease is through vaccination. However, there is an urgent need to establish confidence in the safety of global vaccination efforts, particularly among populations with allergies, as evidence on the adverse effects of SARS-CoV-2 vaccines in this group remains limited. To address this gap, our study aimed to evaluate the safety of inactivated SARS-CoV-2 vaccines in individuals with food and/or drug allergies. The study enrolled a total of 150 participants, who were subjected to a series of questionnaires to evaluate local and systemic reactions within 7 days after each dose. The results revealed that the most prevalent adverse reactions were pain at the injection site (30%) and fatigue (16%) following the initial vaccination. Notably, the incidence of both local and systemic adverse reactions decreased after the second vaccination, which was unexpected. The food allergy and drug allergy subgroups exhibited a similar phenomenon. Furthermore, the incidence of adverse events observed in this study was consistent with the range reported in Phase III clinical trials of inactivated SARS-CoV-2 vaccines. Our findings suggest that individuals with pre-existing food and/or drug allergies have a favorable safety profile when receiving inactivated SARS-CoV-2 vaccination.

S-RBD Antibody Titers Following the First and Second Doses of Inactivated SARS-CoV-2 Vaccination (CoronaVac) in Native Participants: A Prospective Cohort Study in Bali, Indonesia

Background: Vaccination has been recognized as an additional option, besides the health protocols practices to control the coronavirus disease 2019 (COVID-19) pandemic, especially with the unknown specific treatment for the disease. This study sought to evaluate the immunogenicity of CoronaVac among the general population in Bali province, a popular tourist spot in Indonesia. Methods: As many as 422 volunteers were recruited from the three vaccination centers, of which 230 volunteers were seronegative and included in the study. CoronaVac was used as vaccine with dose of 0.5 mL or 3 µg at each administration. Blood samples were drawn before vaccination, 21 days after the first dose, and 56 days after second dose, where the interval between the first and second dose vaccination was 28 days. Vaccine immunogenicity was evaluated by the anti-spike receptor-binding domain (anti-S-RBD) IgG titer which was measured using the electrochemiluminescence immunoassay technique. Results: The mean anti-S-RBD levels at 21 days after first dose, and 21 days after the second dose of vaccination are 25.25 ± 59.74 U/mL and 138.77 ± 90.93 U/mL, respectively. The result of the Friedman test was p <0.001 which means that there are significant differences in anti-S-RBD levels between 21 days after first dose and 21 days after second vaccination. Post hoc analysis with the Wilcoxon test also showed significant difference among the three-testing point (p < 0.001). The seroconversion rate from the first dose of CoronaVac was 69.7% and it increased to 99.4% (171/172) on after the second dose. Conclusion: Although the protective level was not totally reached on the first vaccination, the immunogenicity was considered rapid 3 weeks after the first vaccination.

Safety and Immunogenicity of Homologous and Heterologous Adenoviral-Vectored and mRNA COVID-19 Vaccine Regimens in Radiotherapy Patients

Diminished immune response after vaccination occurs in cancer patients. This observational study evaluated the immune response and safety profile after COVID-19 vaccination in radiotherapy patients. The study comprised 53 cancer patients undergoing radiotherapy and voluntarily received the COVID-19 vaccine. The two regimens were homologous ChAdOx1-S recombinant (AstraZeneca, AZ), "AZ-AZ" and heterologous "AZ-mRNA". The seroconversion rate and anti-RBD immunoglobulin geometric mean titers (GMT) were assessed and compared with healthy controls. Adverse effects were assessed using a questionnaire. The seroconversion rate was 52.4% 1 month after the first dose with GMT 4.3 U/mL (95%CI 1.4-13). Following the second dose, the AZ-AZ group achieved 95% seroconversion rate with GMT = 188.4 U/mL (95%CI 67.1-529), which was significantly lower than the healthy cohort, GMT = 945 U/mL (95%CI 708-1261). Cancer patients in AZ-mRNA group achieved a 100% seroconversion rate with a high GMT = 1400.8 U/mL (95%CI 429.5-4566), which was significantly lower than the healthy cohort, GMT = 5169.9 U/mL (95%CI 3582.2-7461.5). Most adverse effects were mild. Our findings suggest that radiotherapy patients had fair immunogenicity after the first dose, but achieved a high seroconversion rate after the second dose with manageable adverse effects. However, their immunologic response was lower than in healthy individuals, indicating that other preventive strategies are needed.

CoronaVac, BNT162b2 and heterologous COVID-19 vaccine outcomes in patients with ventricular assist device

BACKGROUND

A consensus has not yet been reached regarding which COVID-19 vaccine program should be applied in patients with ventricular assist device (VAD). Our aim was to assess the clinical outcome of inactivated, mRNA and heterologous vaccine program in patient with VAD.

METHODS

In this retrospective and cross-sectional study; adult patients who underwent VAD implantation between January 2012 and September 2021 and received any vaccine that were used in Republic of Türkiye for COVID-19, were included. The patients were divided into three groups according to the type of vaccine; "inactivated," "mRNA" and "heterologous." Clinical outcomes were analyzed.

RESULTS

Eighteen patients were in each group in the "inactivated," "mRNA" and "heterologous" groups. Mean age was 51.6 ± 12 years in "inactivated" group, 42.5 ± 15.5 years in "mRNA" group and 41.1 ± 15.4 years in "heterologous" group. There was no significant difference between the groups in age, gender, body surface area, body mass index and etiology (p > 0.05). After last dose of vaccines, the number of patients had COVID-19 positive test were three (16.7%), one (5.6%), and two (11.1%) in "inactivated," "mRNA" and "heterologous" groups, respectively. Pump thrombosis was seen in two patients in "mRNA" group and one patient in "heterologous" group. No pump thrombosis was seen in "inactivated" group. COVID-19-related death or intubation was not observed.

CONCLUSION

All vaccine that used for COVID-19 are safe and effective in patients with VAD. In countries that give priority to inactivated vaccines, mRNA vaccines may then be made as boosters.

Safety and immunogenicity of heterologous and homologous inactivated and adenoviral-vectored COVID-19 vaccine regimens in healthy adults: a prospective cohort study

In light of intermittent supply shortages of individual vaccines and evidence of rare but serious adverse events after vaccination, heterologous regimens for COVID-19 vaccines have gained significant interest. This study aims to assess the reactogenicity and immunogenicity of the heterologous adenoviral vector (ChAdOx1-S, AstraZeneca; hereafter referred to as AZ) and the inactivated vaccine regimen (CoronaVac; hereafter referred to as CV) in healthy Thai adults immunized between June and September 2021. Our study showed that adverse events following homologous CV-CV and AZ-AZ, and heterologous CV-AZ and AZ-CV combinations, were mild and well tolerated overall. Receptor-binding domain (RBD)-specific antibody responses and neutralizing activities against wild-type and variants of concern after two-dose vaccination were higher in the heterologous CV-AZ and homologous AZ-AZ groups compared to the CV-CV and AZ-CV groups. Conversely, the spike-specific IgA response was detected only in the CV-AZ group after two doses of vaccination. The total interferon gamma response was detected in both the CV-AZ and AZ-CV groups after the two-dose vaccination. Given the shorter completion time of two doses, heterologous CoronaVac followed by ChAdOx1-S can be considered as an alternative regimen to homologous efficacy-proven ChAdOx1-S in countries with circulating variants. Additional studies on the efficacy and durability of immune responses induced by heterologous vaccine regimens are warranted.

Mental health and chest CT scores mediate the relationship between COVID-19 vaccination status and seroconversion time: A cross-sectional observational study in B.1.617.2 (Delta) infection patients

Background

The coronavirus disease (COVID-19) pandemic, which has been ongoing for more than 2 years, has become one of the largest public health issues. Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is one of the most important interventions to mitigate the COVID-19 pandemic. Our objective is to investigate the relationship between vaccination status and time to seroconversion.

Methods

We conducted a cross-sectional observational study during the SARS-CoV-2 B.1.617.2 outbreak in Jiangsu, China. Participants who infected with the B.1.617.2 variant were enrolled. Cognitive performance, quality of life, emotional state, chest computed tomography (CT) score and seroconversion time were evaluated for each participant. Statistical analyses were performed using one-way ANOVA, univariate and multivariate regression analyses, Pearson correlation, and mediation analysis.

Results

A total of 91 patients were included in the analysis, of whom 37.3, 25.3, and 37.3% were unvaccinated, partially vaccinated, and fully vaccinated, respectively. Quality of life was impaired in 30.7% of patients, especially for mental component summary (MCS) score. Vaccination status, subjective cognitive decline, and depression were risk factors for quality-of-life impairment. The chest CT score mediated the relationship of vaccination status with the MCS score, and the MCS score mediated the relationship of the chest CT score with time to seroconversion.

Conclusion

Full immunization course with an inactivated vaccine effectively lowered the chest CT score and improved quality of life in hospitalized patients. Vaccination status could influence time to seroconversion by affecting CT score and MCS score indirectly. Our study emphasizes the importance of continuous efforts in encouraging a full vaccination course.

Antibody dynamics post-Comirnaty and CoronaVac vaccination in Malaysia

Several vaccines have been fast-tracked through clinical trials to mitigate the progression of the SARS‑CoV‑2 pandemic. We analyzed sequential blood samples from 314 recipients of Comirnaty and CoronaVac in East Malaysia for the spike-binding IgG (IgG-S), nucleocapsid-binding IgG (IgG-N), spike-binding IgM (IgM-S) and serum vitamin D (VitD). A subset of samples was analyzed for the neutralizing antibodies (Ig-RBD). Results showed that IgG-S due to Comirnaty was significantly higher than CoronaVac. IgM-S was detected in 80.0% Comirnaty and 69.5% CoronaVac recipients, while IgG-N was detected in 58.1% CoronaVac but not in Comirnaty recipients. All IgG-S-positive vaccines possessed detectable Ig-RBD after the second dose but with a weak to moderate correlation. The serum VitD levels did not influence the antibody magnitude in both vaccines. In essence, SARS-CoV-2 vaccination is an IgG-S-dominant event, Comirnaty was more effective than CoronaVac in mounting IgG-S and Ig-RBD responses, independent of the patient’s VitD level.

Satisfaction with COVID-19 Vaccines in Health Care Workers and the General Population: A Cross-Sectional Study in Urban Bangkok, Thailand

Background: COVID-19 vaccination hesitancy is a global issue. Many people are concerned about experiencing side effects from the vaccine. This study evaluated satisfaction with the COVID-19 vaccine in the general population (GP) and healthcare workers (HCWs) in Bangkok, Thailand. Methods: A cross-sectional online survey was distributed from September-December 2021. Independent sample t-tests were used to compare GP and HCW participants’ total vaccine satisfaction scores as well as their satisfaction with varying vaccine types. Multiple linear regression was used to identify predictors of satisfaction scores among GP and HCWs. Results: A total of 780 valid questionnaire responses were obtained. The majority of GP participants (n = 390) had received their first (93.3%) and second (88.5%) vaccination shots by viral vector vaccine; however, 90% had not received a third dose (booster). In contrast, the majority of HCW participants (n = 390) had received their first (92.8%) and second (82.8%) vaccination doses by the inactivated vaccine, and 83% had received a third vaccine dose. HCWs had significantly higher total satisfaction scores than GP participants (p = 0.034), and they were also significantly more satisfied with the mRNA vaccine as a third dose (p = 0.001). Multiple linear regression models found less association with vaccine satisfaction among GP participants who had not isolated following exposure to COVID-19 and those who have never been at risk of infection (ᵦ −0.159; 95% CI −12.867, −1.877; p = 0.009). Among HCWs, being married (ᵦ 0.157; 95% CI 0.794, 3.278; p = 0.001) or divorced (ᵦ 0.198; 95% CI 3.303, 9.596; p < 0.01) was more closely associated with vaccine satisfaction than being single. Conclusion: HCWs were more satisfied with the type and efficacy of inactivated, viral vector, and mRNA vaccines than GP participants, and the former were also more satisfied with the cost of vaccine boosters. Our results indicate that satisfaction with the COVID-19 vaccine is based on academic knowledge sharing and the government’s promotion efforts. Future research will explore strategies to raise awareness about the importance of vaccination.

Antibody response to SARS-CoV-2 vaccines among hospitalized patients in China: a case-control study

A lack of confidence on the vaccination drive hinders the management of the COVID-19 pandemic. We aimed to assess the antibody response to the SARS-CoV-2 vaccine among hospitalized patients in China. This case-control study was based on SARS-CoV-2 sero-surveillance during hospitalization. From April to June 2021, hospitalized patients without documented COVID-19 infection from the Department of Urology were routinely assayed for anti-SARS-CoV-2 antibodies. The SARS-CoV-2 vaccination history of each participant was obtained from their vaccination records. Of the 405 participants, there were 37 seropositive participants (case group) and 368 seronegative participants (control group); 68 participants (16.8%) had received the inactivated SARS-CoV-2 vaccine, including 54 who received the Sinovac-CoronaVac vaccine and 14 received the Sinopharm vaccine. All seropositive participants who had received one or two doses of the SARS-CoV-2 vaccine were assessed for at least 16 days, while 31 (8.4%) of 368 seronegative controls who had received the vaccine were tested for 1–94 days. The overall seroconversion rate was 54.4% (37/68) in the vaccinated participants who received the inactivated SARS-CoV-2 vaccine. The odds ratio (OR) and confidence interval (CI) for seropositivity was 6.20 (95% CI: 2.05–18.71) in those received full vaccination with two doses versus those partially vaccinated participants with one dose after adjusting for sex and age. These findings imply that the inactivated SARS-CoV-2 vaccine could have a protective antibody response.

The Relationship between Attitudes and Satisfaction Concerning the COVID-19 Vaccine and Vaccine Boosters in Urban Bangkok, Thailand: A Cross-Sectional Study

Background: COVID-19 vaccine hesitancy is a global concern. Many individuals are concerned about the potential side-effects of the COVID-19 vaccine and vaccine boosters. The purpose of this study was to assess attitudes and satisfaction concerning COVID-19 vaccines and vaccine boosters in the population in Bangkok, Thailand. Methods: A cross-sectional online survey measuring COVID-19 vaccine attitudes and satisfaction was distributed from September to December 2021. Multiple linear regression was used to explore associations between demographic variables and questionnaire results. Spearman’s correlation analysis was used to examine associations between attitude and satisfaction scores. Results: A total of 780 questionnaire responses were obtained. The largest groups of participants reported having obtained a first vaccination dose via viral vaccine (52.8%), a second vaccination booster via viral vaccine (49.5%), and a third vaccination booster via mRNA vaccine (28.8%). Multiple linear regression revealed a lower association between vaccine attitude scores and having earned less than a bachelor’s degree (β −0.109; 95% CI −2.541, −0.451) and infection risk without self-isolating (β −0.154; 95% CI −4.152, −0.670) compared with attaining a bachelor’s degree or higher and never having being at risk of infection, respectively. Higher vaccine satisfaction scores were more closely associated with being married than being single (β 0.074; 95% CI −0.073, 3.022), whereas lower vaccine satisfaction scores were less closely associated with non-healthcare workers (β −0.143; 95% CI −4.698, −0.831) and infection risk without self-isolating (β −0.132; 95% CI −6.034, −0.502) compared with non-healthcare workers and never being at risk of infection. There was weak but significant positive correlation between attitude and satisfaction scores (r = 0.338, p-value < 0.001). Hence, a gradual decline in protection following vaccination and the positive effects of a booster dose after primary vaccination have made the decision to administer booster doses. Conclusion: The results suggest that policymakers need to develop more effective strategies to raise awareness about the importance of vaccination.

Immunogenicity of ChAdOx1 nCoV-19 Booster Vaccination Following Two CoronaVac Shots in Healthcare Workers

During the early phase of the COVID-19 pandemic, several countries, including Thailand, provided two shots of CoronaVac to healthcare workers. Whereas ChAdOx1 nCoV-19 is the promising vaccine as the booster dose, the data on immunogenicity when administered after CoronaVac have been limited. The purpose of this study was to evaluate the immunogenicity of ChAdOx1 nCoV-19 as the third dose vaccine in healthcare workers who previously received two shots of CoronaVac. The blood samples were obtained before the third vaccination dose, and one month and three months after vaccination. All participants were measured for humoral immunity including anti-spike IgG and neutralizing antibody by ELISA. Twenty participants were stratified by random samples based on baseline IgG status for a cellular immunity function test at three-month post-vaccination, which included T cell and B cell functions by ELISpot. This study showed significant improvement for both humoral and cellular immunity one month after vaccination. Subgroup analysis indicated a significantly higher neutralizing antibody improvement for the population with a negative anti-spike IgG at baseline. Our study suggests that, while immunity level declines at three months post-vaccination, the level was sufficiently high to protect against SARS-CoV-2.

Safety and Immunogenicity of the Third Booster Dose with Inactivated, Viral Vector, and mRNA COVID-19 Vaccines in Fully Immunized Healthy Adults with Inactivated Vaccine

The coronavirus disease 2019 (COVID-19) pandemic has become a severe healthcare problem worldwide since the first outbreak in late December 2019. Currently, the COVID-19 vaccine has been used in many countries, but it is still unable to control the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, despite patients receiving full vaccination doses. Therefore, we aimed to appraise the booster effect of the different platforms of vaccines, including inactivated vaccine (BBIBP), viral vector vaccine (AZD122), and mRNA vaccine (BNT162b2), in healthy adults who received the full dose of inactivated vaccine (CoronaVac). The booster dose was safe with no serious adverse events. Moreover, the immunogenicity indicated that the booster dose with viral vector and mRNA vaccine achieved a significant proportion of Ig anti-receptor binding domain (RBD), IgG anti-RBD, and IgA anti-S1 booster response. In contrast, inactivated vaccine achieved a lower booster response than others. Consequently, the neutralization activity of vaccinated serum had a high inhibition of over 90% against SARS-CoV-2 wild-type and their variants (B.1.1.7-alpha, B.1.351-beta, and B.1.617.2-delta). In addition, IgG anti-nucleocapsid was observed only among the group that received the BBIBP booster. Our study found a significant increase in levels of IFN-ɣ secreting T-cell response after the additional viral vector or mRNA booster vaccination. This study showed that administration with either viral vector (AZD1222) or mRNA (BNT162b2) boosters in individuals with a history of two doses of inactivated vaccine (CoronaVac) obtained great immunogenicity with acceptable adverse events.