Avoidable COVID-19-related deaths and hospitalizations in Brazil, 2020–2023.

• Despite a very high COVID-19 population-level vaccine effectiveness in 2022, its reduction in the order of 6–8 % in the subsequent year was likely caused by a very low (<10 %) vaccine uptake, leading to a significant upturn in COVID-19 hospitalizations and mortality in the first half of 2023. • Almost 600 lives could have been saved and over 800 hospitalizations avoided had the 2022 vaccination level continued in the first half of 2023. • COVID-19 burden could have also been considerably lower had the vaccination started three months earlier, thus avoiding over 92,000 lives and 277,000 hospitalizations between the start of the epidemic and June 2023. To estimate the number of avoidable COVID-19 deaths and hospitalizations in Brazil. Secondary data on COVID-19 deaths and hospitalizations were related to two measures of cumulative vaccine coverage (in the last six months and before this period) by negative binomial regression to estimate population-level protective effectiveness (PLPE) against severe disease. The latter includes the overall protective effect of all COVID-19-preventive measures, such as direct and indirect vaccine effectiveness, social distancing, and lockdown, but only the vaccine coverage data were available for the regression analysis. COVID-19 mortality rates per 100,000 inhabitants were 10.26, 16.45, 0.14, and 0.94, for the years 2020, 2021, 2022, and the first half of 2023. In the same order and scale, COVID-19 hospitalization rates were 28.96, 47.04, 0.40, and 3.74. Both hospitalizations and deaths peaked early in 2021, then sharply reduced by the end of the year as the first-dose vaccine coverage reached 90 %, and rose with the vaccine coverage within the last six months falling below 10 % in 2023. PLPE for preventing COVID-19 deaths was 19.9 %, 98.9 %, and 93.1 % for the years 2021, 2022, and the first half of 2023. Had Brazil vaccinated the same number of people against COVID-19 in the last quarter of 2020 as it did in the first quarter of 2021, over 117,000 deaths and 277,000 hospitalizations could have been avoided over the period analyzed. PLPE reduction in 2023 was likely caused by low vaccine uptake. The disease burden could have been much lower had the vaccination started earlier and had the vaccine uptake not dropped so sharply in 2023. [ABSTRACT FROM AUTHOR]