Safety and Immunogenicity of COVID-19 BBIBP-CorV Vaccine in Children 3–12 Years Old

Incidence rates of myocarditis and pericarditis within 30 days following homologous and heterologous BNT162b2 vaccinations in individuals 5-40 years of age

INTRODUCTION

Due to the data scarcity in low- and middle-income countries, we aimed to examine the incidence rate of myocarditis and pericarditis within 30 days after each dose of homologous (3 × BNT162b2) and heterologous prime-boost (2 × BBIBP-CorV/BNT162b2) vaccine regimen among individuals younger than 40 years.

METHODS

We conducted a historical control cohort using routinely recorded data from Thai national vaccine and insurance claims databases. Sex-specific incidence rate ratios (IRRs) for myocarditis and pericarditis were calculated for each vaccination strategy and contrasted with incidence rates among the non-immunised population in the pre-COVID-19 period. From August 2021 to September 2022, we tracked the incidence of myocarditis and pericarditis within 30 days after vaccinations using < 40-year-old national population databases. Our reference was the average monthly incidence of these conditions in the non-immunised population from August to October 2019. The exposure of interest was immunisation against the SARS-CoV-2 virus, incorporating the following vaccination strategies: three-dose 3 × BNT162b2 regimen, three-dose 2 × BBIBP-CorV/BNT162b2 regimen, and non-immunisation.

RESULTS

For myocarditis, a total of 215 cases were identified among 7,594,965 individuals in the 3 × BNT162b2 cohort, 5 cases among 2,914,643 individuals in the 2 × BBIBP-CorV/BNT162b2 cohort, and 115 cases among 32,424,780 non-immunised individuals. The sex-specific IRRs (95 % confidence intervals) of myocarditis and pericarditis after the homologous vaccination were 3.09 (1.61, 5.93) and 1.84 (0.72, 4.73) for females and 7.43 (3.11, 17.73) and 10.48 (3.90, 28.15) for males, respectively. Conversely, the IRRs of myocarditis after the heterologous vaccination were not significant (females: 2.24 (0.70, 7.17); males: 1.99 (0.48, 8.21)). IRRs could not be obtained for pericarditis after the heterologous vaccination because of the small number of observed events.

CONCLUSIONS

The study observed a significantly increased risk of myocarditis and pericarditis following homologous 3 × BNT162b2 vaccination but had insufficient power to confirm an increased risk for myocarditis following the heterologous prime-boost 2 × BBIBP-CorV/BNT162b2 vaccination. The incidence of pericarditis following the heterologous vaccination was too rare to evaluate.

Efficacy and effectiveness of inactivated vaccines against symptomatic COVID-19, severe COVID-19, and COVID-19 clinical outcomes in the general population: a systematic review and meta-analysis

Background

Inactivated, whole-virion vaccines have been used extensively in the SARS-CoV-2 pandemic. Its efficacy and effectiveness across regions have not been systematically evaluated. Efficacy refers to how well a vaccine performs in a controlled environment. Effectiveness refers to how well it performs in real world settings.

Methods

This systematic review and meta-analysis reviewed published, peer-reviewed evidence on all WHO-approved inactivated vaccines and evaluated their efficacy and effectiveness against SARS-CoV-2 infection, symptomatic infection, severe clinical outcomes, and severe COVID-19. We searched Pubmed (including MEDLINE), EMBASE (via OVID), Web of Science Core Collection, Web of Science Chinese Science Citation Database, and Clinicaltrials.gov.

Findings

The final pool included 28 studies representing over 32 million individuals reporting efficacy or effectiveness estimates of complete vaccination using any approved inactivated vaccine between January 1, 2019 and June 27, 2022. Evidence was found for efficacy and effectiveness against symptomatic infection (OR 0.21, 95% CI 0.16-0.27, I2 = 28% and OR 0.32, 95% CI 0.16-0.64, I2 = 98%, respectively) and infection (OR 0.53, 95% CI 0.49-0.57, I2 = 90% and OR 0.31, 95% CI 0.24-0.41, I2 = 0%, respectively) for early SARS-CoV-2 variants of concern (VoCs) (Alpha, Delta), and for waning of vaccine effectiveness with more recent VoCs (Gamma, Omicron). Effectiveness remained robust against COVID-related ICU admission (OR 0.21, 95% CI 0.04-1.08, I2 = 99%) and death (OR 0.08, 95% CI 0.00-2.02, I2 = 96%), although effectiveness estimates against hospitalization (OR 0.44, 95% CI 0.37-0.53, I2 = 0%) were inconsistent.

Interpretation

This study showed evidence of efficacy and effectiveness of inactivated vaccines for all outcomes, although inconsistent reporting of key study parameters, high heterogeneity of observational studies, and the small number of studies of particular designs for most outcomes undermined the reliability of the findings. Findings highlight the need for additional research to address these limitations so that more definitive conclusions can be drawn to inform SARS-CoV-2 vaccine development and vaccination policies.

Funding

Health and Medical Research Fund on COVID-19, Health Bureau of the Government of the Hong Kong SAR.

Post-vaccination SARS-CoV-2 seroprevalence in children aged 3-11 years and the positivity in unvaccinated children: A retrospective, single-center study

OBJECTIVE

To analyze the positivity and levels of SARS-CoV-2 antibodies in vaccinated children to evaluate the humoral immune response of vaccination on pediatric population. Analysis on the causes of antibody positivity in unvaccinated children.

METHODS

A retrospective study was conducted on children who were admitted to the Children's Hospital Affiliated to Capital Institute of Pediatrics. The clinical data of serological testing of SARS-CoV-2 immunoglobulin M (IgM) and IgG antibodies were collected from SARS-CoV-2 vaccinated or unvaccinated children with no evidence of prior novel coronavirus infection. Chemiluminescence immunoassay was utilized for the in vitro determination of SARS-CoV-2 antibodies.

RESULTS

A total of 3,321 healthy children aged 6-11 years received two doses of inactivated SARS-CoV-2 vaccine. At 1 month after the second dose, the positive rate (96.5%) and levels [8.039 (interquartile range (IQR), 6.067-9.098)] of SARS-CoV-2 IgG antibodies reached the peak and remained at a high level for 2-3 months, after which the positive rate and level of vaccine-induced IgG antibody gradually decreased. Compared with 1 month after the second dose of vaccine, the positive rate of IgG antibody decreased to 70.4% at 7 months, and the antibody level decreased by 69.0%. A total of 945 children aged 3-5 years received one or two doses of inactivated vaccine. The positive rate and levels of SARS-CoV-2 IgG antibody in participants remained high for 3 months after vaccination. There was no gender-based difference in positive rate of IgG antibody in children aged 3-11 years old (P>0.05). Among the 5,309 unvaccinated children aged 0 day to 11 years, 105 (2.0%) were positive for SARS-CoV-2 IgG antibody, which was associated with passive infusion. The maternal humoral response to COVID-19 vaccination in noninfected pregnant women was transferred through the placenta to the fetus, and some children obtained SARS-CoV-2-positive antibodies through blood transfusion.

CONCLUSIONS

Inactivated SARS-CoV-2 vaccines could induce robust humoral immune response that gradually declined within several months after the second dose. Therefore, it helps to determine whether children receive a booster dose and elicit a long-term memory immune response. Positive SARS-CoV-2 antibodies in unvaccinated children were associated with passive IgG antibody infusion.