Peer-reviewed article
Effectiveness of BNT162B2 and CoronaVac vaccines in reducing COVID-19 severity among children aged 3-4 years in Brazil.
Marina Coelho de Padua, Marcos Otávio Brum Antunes, Renato T Stein, Leonardo A Pinto, Marcus H Jones et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined how well two COVID-19 vaccines protected children aged 3-4 years in Brazil from severe COVID-19 during the Omicron wave in 2022-2023. Using national health data, researchers compared hospitalization and mechanical ventilation rates between vaccinated and unvaccinated children. Vaccination reduced the risk of hospitalization by 79% after one dose and 49% after two doses, and protected against the need for ventilators in most cases. No vaccinated children died from COVID-19 during the study period.
Key points
- Vaccine effectiveness against hospitalization was 79.0% after one dose and 49.2% after two doses of CoronaVac
- Effectiveness against invasive mechanical ventilation was 77.6% after one dose and 79.1% after two doses
- No deaths occurred among fully vaccinated children during the study period
- Only 15% of children aged 3-4 years in Brazil completed the CoronaVac primary series by the end of the study
- CoronaVac was the predominant vaccine used in this age group, with very limited BNT162b2 coverage (2%)
Limitations
The study could not compare the two vaccines directly because so few children in Brazil received BNT162b2. The findings may not apply to other COVID-19 variants or vaccine formulations.
Abstract
INTRODUCTION: National population-based databases from large countries can provide real-world estimates of COVID-19 vaccine effectiveness. This analysis examined the effectiveness of BNT162b2 and CoronaVac against severe COVID-19-related outcomes in children aged 3 to 4 years during the Omicron phase of the pandemic in Brazil. METHODS: This nationwide population-based cohort study assessed incidence rate ratios for hospitalization due to COVID-19-associated severe acute respiratory syndrome, invasive ventilatory support, and death among children aged 3 to 4 years, according to vaccination status (unvaccinated, 1 dose, or 2 doses), during 2022-2023. The study period spanned epidemiological weeks 31-52 of 2022 and weeks 1-13 of 2023. Data on laboratory-confirmed COVID-19-related hospitalizations, clinical outcomes, and vaccination status were obtained from OpenDATASUS, and vaccination coverage was estimated using data from the Brazilian Ministry of Health COVID-19 vaccination dashboard. RESULTS: Among children aged 3 to 4 years completion of the primary series increased to 15% for CoronaVac and 2% for BNT162b2 during the study period, corresponding to 797,956 and 79,650 individuals receiving the second dose, respectively. A total of 963 children were hospitalized with COVID-19-associated severe acute respiratory syndrome. Vaccine effectiveness against hospitalization was 79.0% (95% CI, 69.9%-85.4%) after partial vaccination and 49.2% (95% CI, 32.5%-61.9%) after completion of the primary series (p < 0.01). Effectiveness against invasive mechanical ventilation was 77.6% and 79.1%, respectively; no deaths occurred among fully vaccinated children. Direct comparisons between vaccines were not feasible because of the lower proportion of BNT162b2 recipients. CONCLUSIONS: COVID-19 vaccination, predominantly based on the CoronaVac vaccine, was associated with a significant reduction in severe outcomes among children aged 3-4 years, providing robust evidence to support pediatric immunization strategies and public health efforts.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- COVID-19 vaccination with BNT162b2 or CoronaVac vaccines, delivered as partial series (1 dose) or complete primary series (2 doses)
- Population
- Children aged 3 to 4 years in Brazil during the Omicron phase (epidemiological weeks 31-52 of 2022 and weeks 1-13 of 2023)
Key finding
Vaccine effectiveness against hospitalization was 79.0% (95% CI 69.9%-85.4%) after one dose and 49.2% (95% CI 32.5%-61.9%) after two doses
Padua et al. · PubMed (US National Library of Medicine) · 28 Jul 2026