IMPACT OF COVID-19 VACCINATION ON SARI LETHALITY AMONG OLDER ADULTS IN BRAZIL: AN ECOLOGICAL STUDY (2020–2023)

Introduction: Severe Acute Respiratory Syndrome (SARI) became one of the main causes of hospitalization and death among older adults during the coronavirus pandemic (COVID-19), especially due to the greater severity of infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this group. With the start of COVID-19 vaccination in Brazil in January 2021, prioritizing older adults, a reduction in severe outcomes was expected. This study aimed to assess the trend in hospital lethality from SARI caused by COVID-19 among Brazilian older adults between 2020 and 2023, and its relationship with vaccination coverage against SARS-CoV-2. Methods: This is a retrospective ecological study that analyzed public data from 2020 to 2023 on hospitalizations for SARI caused by SARS-CoV-2 among older adults (≥60 years). Lethality by age group was calculated and related to vaccination coverage (complete primary series and booster doses) obtained from OpenDataSUS. A descriptive analysis of the annual evolution of lethality and vaccination was performed. Results: In 2020, before vaccination, lethality from COVID-19–related SARI among older adults was 47.2%. In the following year, with the start of immunization, the rate dropped to 35.6%. In 2022 and 2023, with expansion of vaccine schedules and boosters, stabilization was observed between 24% and 26%. Vaccination coverage with complete primary series reached 87% of older adults in 2021, increasing to more than 95% in 2022. The introduction of booster doses coincided with the maintenance of lower levels of lethality, even with circulation of the Delta and Omicron variants. The data suggest an inverse association between vaccination coverage and hospital lethality from SARI among older adults over the years analyzed. Conclusion: COVID-19 vaccination significantly reduced lethality from SARI among older adults in Brazil between 2020 and 2023. The findings confirm its effectiveness against severe forms, even in the face of new variants, especially with the administration of booster doses. High vaccination coverage, together with surveillance and hospital strengthening, contributed to the decline in mortality. Despite the limitations of aggregated data, standardization of SIVEP-Gripe strengthens the analysis. Continued vaccination and surveillance are essential to prevent new outbreaks.