Immunogenicity and safety of CoronaVac in children in an immuno-bridging phase 3 clinical trial

Abstract

Abstract Several clinical trials demonstrated that CoronaVac had favorable efficacy and immunogenicity in adults and children. This phase 3, open-label, immuno-bridging clinical trial assessed the superior immunogenicity of CoronaVac in Chinese children aged 3–11 years compared to Brazilian adults aged 18–26 years, and its non-inferiority in Chinese children compared to overseas children (NCT05137418). A sample size of 1000 healthy children aged 3–11 years were enrolled in China. Two doses of CoronaVac were given 28 days apart. Superiority and non-inferiority analysis were conducted by assessing the neutralizing antibodies titers against SARS-CoV-2. The geometric mean titer (GMT) of neutralizing antibodies in Chinese children on day 28 post second dose vaccination was 198.47 (95%CI 189.44-207.93), superior to that of the Brazilian adults (62.52, 95%CI 54.99–71.08) with the adjusted GMT ratio of 3.18 (95%CI 2.85–3.54); and it was non-inferior compared to the overseas children (202.58, 95%CI 166.29–246.80) with the adjusted GMT ratio of 0.98 (95%CI 0.85–1.13) and seroconversion rate difference of 0.00% (95%CI -0.44-2.58). Most adverse reactions were mild and moderate. All of the serious adverse events (SAEs) were considered unrelated to vaccination. CoronaVac showed good immunogenicity and safety in children aged 3–11 years. The results suggested that CoronaVac could have favorable protection against COVID-19 in children.