In-hospital case fatality ratio due to COVID-19 in four Brazilian state capitals and its possible temporal relationship with the Gamma variant, 2020-2021.

Objective: To describe in-hospital and intensive care unit (ICU) case fatality ratios due to COVID-19 in four Brazilian state capitals, during the months of epidemic peaks and previous months.

Methods: This was an ecological study using monthly data from the Influenza Epidemiological Surveillance Information System, between 2020-2021, in individuals aged 20 years or older. Case fatality ratio and mortality rate were estimated with 95% confidence intervals (95%CI).

Results: In Manaus, the capital city of the state of Amazonas, ICU case fatality ratio among those >59 years old was lower in December/2020 (80.9%; 95%CI 78.4;83.3) and during the peak in January/2021 (79.9%; 95%CI 77.4;82.5), compared to the peak in April/2020 (88.2%; 95%CI 86.1;90.3). In São Paulo, the capital city of the state of São Paulo, Curitiba, the capital city of the state of Paraná, and Porto Alegre, the capital city of the state of Rio Grande do Sul, there was a decrease or stability in ICU and in-hospital case fatality ratio in January/2021, compared to the reference month in 2020.

Conclusion: In January/2021, in-hospital and ICU case fatality ratios decreased or remained stable in the four state capitals, especially in Manaus, and during the epidemic peak with the prevalence of the Gamma variant.