Vaccine effectiveness of CoronaVac against symptomatic and severe COVID-19 among children in Brazil during the Omicron period

Abstract

Compared to previous variants, the SARS-CoV-2 B.1.1.529 (Omicron) variant has relatively high infection rates, including among children. Even though severe COVID-19 in children is rare, this group is susceptible to the multisystem inflammatory syndrome in Children (MIS-C), long-COVID and downstream effects of COVID-19, including social isolation and education disruption. There is evidence that vaccination with an mRNA vaccine offers protection against infection and severe forms of COVID-19 for children. However, data on the effectiveness of inactivated virus vaccine, the most used platform worldwide, is scarce during the Omicron period. In Brazil, children between 6 to 11 years are eligible to receive the CoronaVac vaccine. Using a national linked database from January 21, 2022, up to April 19, 2022, during the Omicron dominant period in Brazil, we conducted a test-negative design with 194,258 tests to assess CoronaVac effectiveness against infection and severe (hospitalisation or death) outcomes among children aged 6 to 11 years. The estimated VE for symptomatic infection was 35.0% (95% CI 27.7–41.5) at 0–13 days and 41.5% (95% CI: 34.4–47.7) at ≥ 14 days post-second dose. For severe outcomes (hospitalisation or death) VE was 69.2% (95% CI: 11.7–93.6) at 0–13 days and 63.5% (95% CI: 5.8–90.0). Two doses of CoronaVac in children during the Omicron period showed low levels of protection against symptomatic infection, and modest levels against severe illness.

Human Vaccines & Immunotherapeutics: News May 2022

“…In contrast, the effectiveness of the CoronaVac vaccine (Sinovac) is only 40% against symptomatic disease in children, according to two studies from Latin America. 3 , 4 At the same time, the Chinese-produced vaccine prevented 65–70% of hospitalizations.…”

Humoral and Cellular Immunogenicity and Safety of 3 Doses of CoronaVac and BNT162b2 in Young Children and Adolescents with Kidney Diseases

“…3,4 CoronaVac is a whole-virus inactivated vaccine with robust immunogenicity and real-world effectiveness demonstrated in children aged 3-17 years. [5][6][7][8] In many places, including Hong Kong, immunocompromised children and adolescents are recommended to receive a 3-dose mRNA or inactivated vaccine primary series, due to their clinical vulnerability and suboptimal immunogenicity. 9 We have previously shown that the antibody responses elicited by 2 doses of BNT162b2 were diminished in adolescents with kidney diseases.…”