Trends in the prevalence of COVID-19 infection in Rio Grande do Sul, Brazil: repeated serological surveys. SciELO Preprints, 2020. DOI: 10.1590/SciELOPreprints.41. Disponível em: https://preprints.scielo.org/index.php/scielo/preprint/view/41. Acesso em: 8 nov. 2026.