Population-based seroprevalence of SARS-CoV-2 and the herd immunity threshold in Maranhão

ABSTRACT OBJECTIVE: To estimate the seroprevalence of SARS-CoV-2 in the state of Maranhão, Brazil. METHODS: A population-based household survey was performed, from July 27, 2020 to August 8, 2020. The estimates considered clustering, stratification and non-response. Qualitative detection of IgM and IgG antibodies was performed in a fully-automated Elecsys® Anti-SARS-CoV-2 electrochemiluminescence immunoassay on the Cobas® e601 analyzer (Roche Diagnostics). RESULTS: In total, 3,156 individuals were interviewed. Seroprevalence of total antibodies against SARS-CoV-2 was 40.4% (95%CI 35.6-45.3). Population adherence to non-pharmaceutical interventions was higher at the beginning of the pandemic than in the last month. SARS-CoV-2 infection rates were significantly lower among mask wearers and among those who maintained social and physical distancing in the last month compared to their counterparts. Among the infected, 26.0% were asymptomatic. The infection fatality rate (IFR) was 0.14%, higher for men and older adults. The IFR based on excess deaths was 0.28%. The ratio of estimated infections to reported cases was 22.2. CONCLUSIONS: To the best of our knowledge, the seroprevalence of SARS-CoV-2 estimated in this population-based survey is one of the highest reported. The local herd immunity threshold may have been reached or might be reached soon.

Bibliographic Details

Main Authors:	Silva,Antônio Augusto Moura da, Lima-Neto,Lídio Gonçalves, Azevedo,Conceição de Maria Pedrozo e Silva de, Costa,Léa Márcia Melo da, Bragança,Maylla Luanna Barbosa Martins, Barros Filho,Allan Kardec Duailibe, Wittlin,Bernardo Bastos, Souza,Bruno Feres de, Oliveira,Bruno Luciano Carneiro Alves de, Carvalho,Carolina Abreu de, Thomaz,Erika Barbara Abreu Fonseca, Simões-Neto,Eudes Alves, Leite Júnior,Jamesson Ferreira, Cosme,Lécia Maria Sousa Santos, Campos,Marcos Adriano Garcia, Queiroz,Rejane Christine de Sousa, Costa,Sérgio Souza, Carvalho,Vitória Abreu de, Simões,Vanda Maria Ferreira, Alves,Maria Teresa Seabra Soares de Brito e, Santos,Alcione Miranda dos
Format:	Digital revista
Language:	English
Published:	Faculdade de Saúde Pública da Universidade de São Paulo 2020
Online Access:	http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0034-89102020000100306
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