The Sinovac COVID vaccine shows moderate efficacy against SARS-CoV-2 infection in children aged 3 to 5 years

A new study reviewed by the Nature Portfolio Journal and published on a preprint server Research Square *, Researcher surveyed Effectiveness of CoronaVac, a coronavirus disease 2019 (COVID-19) vaccine developed by Sinovac Biotech, is intended for children aged 3 to 5 years.

The results of this study show that the two-dose vaccine regimen is very effective in preventing severe COVID-19, whereas this vaccine regimen is reasonably effective in preventing infection. increase.

study: Efficacy of CoronaVac in children 3-5 years of age during the development of Omicron SARS-CoV-2. Image Credit: didesign021 / Shutterstock.com

Background

The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused unprecedented damage to the global medical system, with more than 468 million infections worldwide. , About 6.1 million deaths have been reported. The highest severity of COVID-19 has been observed between the elderly and those with comorbidities. In contrast, SARS-CoV-2 caused asymptomatic or mild infections primarily in children.

The recent emergence of SARS-CoV-2 omicron variants has led to a significant resurgence of COVID-19 cases worldwide due to their high contagiousness and antigenic escape capacity. In addition to significantly increasing the number of cases of breakthrough infections with the vaccine, the Omicron variant also increased the infection and hospitalization rates of children. The increased susceptibility of children to Omicron infection emphasizes the need to assess the vaccine efficacy of children.

Research design

A total of 490,694 children were enrolled in the current study, all receiving CoronaVac twice at 28-day intervals. Vaccine efficacy was assessed for laboratory-confirmed COVID-19, hospitalization, and intensive care unit (ICU) admissions.

In addition, vaccine efficacy was assessed using a reverse-probability weighted survival regression model that estimates the hazard ratio of complete immunization to deimmunization. This study was conducted between December 2021 and February 2022. This is the time when Omicron variants were prevalent mainly in Chile.

Survey results

During the outbreak of Omicron, CoronaVac showed 38% efficacy against SARS-CoV-2 infection in children aged 3 to 5 years. Vaccines were associated with 64% and 69% efficacy, respectively, for COVID-19-related admissions and prevention of ICU admissions.

The vaccine efficacy observed in the current study is significantly lower than that observed in previous studies that estimated the efficacy of CoronaVac in children 6-16 years of age at the time of delta outbreak. The study estimated that vaccine efficacy was 74%, 91%, and 93% for SARS-CoV-2 infection, hospitalization, and ICU admission, respectively.

This difference in vaccine efficacy may be due to the higher antigenic escape capacity of the Omicron mutant compared to the Delta mutant. Another reason could be that the current research group includes relatively young children. In this regard, studies have shown that the age of a child can affect the effectiveness of the vaccine.

Scientists have adjusted research estimates of observable clinical, demographic, and socio-economic contaminating factors that may affect the vaccination process and the risk of COVID-19. However, it was not possible to coordinate findings on unobservable confounding factors, such as adherence to the COVID-19 protocol by vaccinated and unvaccinated children and their parents. These factors can also affect the estimated vaccine efficacy.

Conclusion

Current studies provide actual estimates of the efficacy of the inactivated virus COVID-19 vaccine in children aged 3 to 5 years. This vaccine is moderately effective in preventing SARS-CoV-2 infection. Although it seems to be very effective against severe COVID-19.

The current study was conducted during the outbreak of Omicron in Chile. This was a period of rapid vaccine deployment and high intake rates. In summary, the actual estimates provided here may complement the estimates made in controlled clinical trials and provide valuable information to policy makers for risk / benefit analysis and decision-making processes. there is.

*Important Notices

Research Square Publish preliminary scientific reports that should not be considered definitive as they have not been peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.