Prevalence evolution of SARS-CoV-2 infection in the city of São Paulo, 2020–2021
Authors: Albuquerque José Olimpio Moura de , Kamioka Gabriela Akemi , Madalosso Geraldine , Costa Selma Anequini , Ferreira Paula Bisordi , Pino Francisco Alberto , Sato Ana Paula Sayuri , Carvalho Ana Carolina Aguiar de , Amorim Ana Beatriz Pagliaro , Aires Caroline Cotrim , Kataoka Ana Paula Arruda Geraldes , Savani Elisa San Martin Mouriz , Bessa Thirsa Alvares Franco , Aguiar Breno Souza de , Failla Marcelo Antunes , Santos Edson Aparecido dos , Brito Edjane Maria Torreão , Santos Maria Cristina Honório dos , Saboia e Silva Solange Maria , Caldeira Luiz Artur Vieira , Zamarco Luiz Carlos , Fonseca Sandra Maria Sabino , Lima Marcia Maria de Cerqueira , Marques Ivanilda Argenau , Silva Fabiana Érica Vilanova da , Glasser Paula Regina , Burihan Patrícia Carla Piragibe Ramos , Cavazzana Cinthya Luzia , Mello Debora Silva de , Pellini Alessandra Cristina Guedes , Nishio Fernando Yoshiki , Kian Fernanda Miyashiro , Braga Elza de Santana , Bertelli Nilza Maria Piassi , Fracini Wagner , Gonçalves Marcelo Dell Áquila , Zular Paulete Secco , Piva Regiane de Santana , Masi Eduardo 
Published: October 2021

OBJECTIVE To estimate the evolution of the prevalence of SARS-CoV-2 virus infection among residents aged 18 years or over in the municipality of São Paulo. METHODS This is a population-based household survey conducted every 15 days, between June and September 2020, and January and February 2021. In total, the study comprised 11 phases. The presence of antibodies against SARS-CoV-2 was identified in venous blood using a lateral flow test, Wondfo Biotech. In the last phase, the researchers combined it with an immunoenzymatic test, Euroimmun. The participants also answered a semi-structured questionnaire on sociodemographic and economic factors, and on social distancing measures. Prevalence estimates and the 95% confidence interval were estimated according to regions, Human Development Index, sex, age group, ethnicity, education, income, and variables associated with risk or prevention of infection. To compare the frequencies among the categories of each variable, the chi-square test with Rao-Scott correction was used, considering a significance level of 5%. RESULTS In total, 23,397 individuals were interviewed and had their samples collected. The estimated prevalence of antibodies against SARS-CoV-2 ranged from 9.7% (95%CI: 7.9–11.8%) to 25.0% (95%CI: 21.7–28.7). The prevalence of individuals with antibodies against the virus was higher among black and brown people, people with lower schooling and income, and among residents of regions with lower Human Development Index. The lowest prevalences were associated with recommended measures of disease protection. The proportion of asymptomatic infection was 45.1%. CONCLUSION The estimated prevalence of the infection was lower than the cumulative incidence variation, except for the last phase of the study. The differences in prevalence estimates observed among subpopulations showed social inequality as a risk of infection. The lower prevalence observed among those who could follow prevention measures reinforce the need to maintain social distancing measures as a way to prevent SARS-CoV-2 infection.