Effectiveness of BNT162b2 and CoronaVac against COVID-19-related severe outcomes among children and adolescents: A Brazilian nationwide cohort study

Introduction: Nationwide databases from large countries may provide real-world evidence about COVID-19 vaccine effectiveness (VE). This study sought to assess the VE of BNT162b2 and CoronaVac against COVID19-related severe outcomes in school-aged children and adolescents during the Omicron wave of the COVID19 pandemic in Brazil. Methods: A nationwide population-based cohort study compared the incidence risk ratios (IRRs) of hospitalization due to COVID-19-associated severe acute respiratory syndrome (SARS), need for invasive ventilatory support, and death among school-aged children (age 5 to 11 years) and adolescents (age 12 to 17 years), stratified by vaccination status (none, one, or two doses), in 2022. The period included epidemiological weeks (EW) 10 to 34 for school-aged children and EW 1 to EW 22 for adolescents. Data from all individuals hospitalized due to laboratory-confirmed COVID-19-related SARS were extracted from OpenDATASUS, where individual data including clinical outcomes and vaccination status are available. Vaccine coverage was estimated using data from the Brazilian Ministry of Health "Vacinometro COVID-19" dashboard. Results: An eligible population of 19,219,424 school-aged children and 22,580,918 adolescents was assessed. For school-aged children, the VE against hospitalization for SARS, invasive ventilatory support, and death after one and two doses was 61 % and 58 %, 62 % and 74 %, and 81 % and 88 %, respectively (all p < 0.01). Among adolescents, the VE against the same outcomes after one and two doses was 55 % and 72 %, 60 % and 78 %, and 83 % and 80 %, respectively (all p < 0.05). CoronaVac was noninferior to BNT162b2 considering all outcomes among fully vaccinated school-aged children, a group that could have received either of the two vaccines. Conclusions: COVID-19 vaccines are effective against severe outcomes in school-aged children and adolescents and are protective against mortality even after a single dose. CoronaVac was not inferior to BNT162b2 in schoolaged children.