The inactivated COVID-19 vaccine CoronaVac®, innovated and manufactured by Sinovac Biotech LTD. (SINOVAC), has been widely used in Chilean minors since September 2021. Recently, an interim safety and immunogenicity analysis in Chile of an international multicenter, randomized, double-blind, placebo-controlled phase III clinical study was published on the preprint platform MedRxiv to evaluate safety, immunogenicity, and efficacy of CoronaVac® in Chilean children and adolescents aged 3-17 years old.
Between September 2021 and December 2021, a total of 963 Chilean adolescent volunteers aged 3-17 participated in the study. The results of this preliminary analysis show that children and adolescents aged 3-17 are safe after being vaccinated with CoronaVac®, and the humoral immunity and specific T cells induced by the vaccine can protect against new coronavirus infection and severe disease, and neutralize Antibodies recognize Delta and Omicron variants.
In children and adolescents aged 3-17, neutralizing antibody titers to COVID-19 increased significantly after two doses of CoronVac®, and antibody levels were higher than in adults1. Among them, the antibody level of children aged 3-11 was slightly higher than that of teenagers aged 12-17. In addition, the seropositivity of both groups reached 100% 4 four weeks after the second dose of CoronaVac®.
CoronaVac® immunization induces anti-S1-RBD antibodies with neutralizing capacities in children and adolescents.
Furthermore, the study discovered that two doses of CoronaVac® induce a robust activation and memory population of CD4+ T cells in children and adolescents.
Changes in activation-induced markers (AIMs) expression in CD4+ T cells specific for SARS-CoV-2 after two doses of CoronaVac® in children and adolescents.
Neutralizing antibodies and specific T cells generated in children and adolescents aged 3-17 after inoculation with two doses of CoronaVac® can recognize the Delta and Omicron variants of the SARS-CoV-2, showing good cross-neutralization. Notably, the immune response to the Omicron variant was stronger than the original strain.
CoronaVac was well tolerated in 3-17 participants, and the incidence of adverse events after vaccination was low. NO vaccine-related serious adverse events were reported.
The dosage form of CoronaVac used in this study is the same as that of an adult. Previous studies have shown that 3-17-year-olds vaccinated with CoronaVac induces higher levels of neutralizing antibodies than adults and older adults2. Based on a previous real-world study of more than 2 million children in Chile, CoronaVac was 74.5% protective against symptomatic infection in minors 6-16 years old, 91%2 protective against hospitalized cases, and 91% protective against hospitalized cases. The protective effect of ICU hospitalized cases was 93.8%3 .
Up to now, SINOVAC has supplied more than 2.7 billion doses of CoronaVac to the world and has provided protection for minors in 13 countries and regions. There are 250 million doses administered among children aged 3-17 in China have been vaccinated with CoronaVac, SINOVAC will continue to safeguard the health of children and adolescents around the world.
Soto, Jorge A., et al. "An inactivated SARS-CoV-2 vaccine is safe and induces humoral and cellular immunity against virus variants in healthy children and adolescents in Chile." medRxiv (2022). https://www.medrxiv.org/content/10.1101/2022.02.15.22270973v1
Kung Y-A, Huang C-G, Huang S-Y, et al. Antibody titers measured by commercial assays are correlated with neutralizing antibody titers calibrated by international standards. medRxiv 2021;2021.07.16.21260618.
Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy children and adolescents: a double-blind, randomised, controlled, phase 1/2 clinical trial.
Jara, Alejandro, et al. Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Children and Adolescents: A Large-Scale Observational Study. SSRN（2022）. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4035405