Prevalence evolution of SARS-CoV-2 infection in the city of São Paulo, 2020–2021

Abstract

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.

Seroepidemiology of SARS-CoV-2 on a partially vaccinated island in Brazil: Determinants of infection and vaccine response

“…Compared to surveys conducted in Brazil around mid-2021 the seroprevalence of antibodies against SARS-CoV-2 in our sample (53.61%) was higher than other studies reported in the South and Southeast regions of Brazil ( 14 , 16 , 17 ), being closer to rates observed at that time in the North region ( 18 , 19 ) and in indigenous populations ( 20 , 21 ). With a vaccine coverage of 37% in our study population, the large difference in seroprevalence between vaccinated (90.5%) and unvaccinated (31%) residents confirmed findings from other studies ( 22 ) of how vaccination decisively contributes to the population's immunity, even in an area with a high prevalence of infection-induced antibodies after exposure to a pandemic for more than a year.…”

Hospitalization and bed occupancy rate in a COVID-19 intensive care unit

“…Em relação à distribuição dos casos de CO-VID-19 ao longo de um ano de estudo, houve um número considerável de notificações de casos novos, sendo o mês de março de 2021 o responsável por maiores quantidades de casos notificados e junho de 2020 o de menor quantidade, com diferenças estatisticamente significativas (p<0,001). Isso difere da pesquisa realizada no município de São Paulo (SP), com 23.397 participantes e amostras dos meses de junho a setembro de 2020, em que o período entre 16 a 18 de fevereiro de 2021, foi responsável pelo maior número de casos confirmados de COVID-19 e de 22 a 24 de setembro de 2021, menor número de casos 21 . Ainda, em um outro estudo realizado em Uberlândia (MG), no período de 21 de março a 7 agosto de 2020, foram notificados 14.389 casos confirmados, apresentando contínuo aumento dos casos 22 , o que diferente também do município estudado, o qual apresenta osci-lações no padrão de casos confirmados.…”