A seroprevalence survey of anti-SARS-CoV-2 antibodies among individuals 18 years of age or older living in a vulnerable region of the city of São Paulo, Brazil

Abstract

A second wave of COVID-19 has demonstrated how challenging it will be to achieve sustained control of the disease, even with vaccination underway in many countries. Therefore, it remains relevant to keep improving our understanding of the distribution of COVID-19, especially of asymptomatic individuals, among different populations, and particularly in vulnerable regions. Hence, this population-based serosurvey had the objective of estimating the prevalence of individuals 18 years of age or older infected by SARS-CoV-2, and the proportion of asymptomatic individuals, among a vulnerable population living in an urban setting. This was a cross-sectional single-stage cluster sampling serosurvey conducted between September and December of 2019, in a vulnerable region of the city of São Paulo, Brazil. Families covered by three public primary healthcare units represented the selected clusters. After study inclusion, participants were asked about signs and symptoms related to COVID-19, and had collected 10 mL of blood for serology testing. A total of 272 individuals from 185 families were included in the study, out of the 400 eligible individuals for inclusion, resulting in a non-response rate of 32%. The post stratified prevalence of individuals infected by SARS-CoV-2 was 45.2% (95% CI: 39.4–51.0%), with a proportion of asymptomatic cases of 30.2% (95% CI: 23.3–38.0%). This population-based serosurvey identified a greater prevalence of infected individuals by SARS-CoV-2 compared to data from the beginning of the pandemic, and from a recent citywide serosurvey, with a similar proportion of asymptomatic individuals. It demonstrated the value of primary healthcare services for disease surveillance activities, and the importance of more focused serosurveys, especially in vulnerable locations, and the need to evaluate new surveillance strategies to take into account asymptomatic cases.

Prevalence and predictors of anti-SARS-CoV-2 serology in a highly vulnerable population of Rio de Janeiro: A population-based serosurvey

“… 40 In a vulnerable area in Sao Paulo city (Paraisópolis), a 43·8% prevalence was found among individuals aged 18 years or older ( n = 272) (from September to December 2020). 41 Moreover, a prospective cohort study conducted in the same neighbourhood as our study estimated the incidence of COVID-19 during four waves (from May 2020 to Nov 2021) and found that the incidence was much higher than previously reported by similar studies in the US and that the incidence was the highest in the first wave (May through November 2020). 42 These results suggest that the burden of COVID-19 is highly unequal, impacting to a much higher degree vulnerable and marginalized populations.…”

SARS-CoV-2 testing among patients and healthcare professionals in an HIV outpatient clinic in Brazil

“…In another study in a large university clinic in the region, using the same RDT, 13.9% of 439 outpatients July 2020 tested positive 14 . An evaluation using the ECLIA assay on vulnerable populations of the metropolitan area, showed higher rates, 43.8% (95% CI: 37.7-50%) 15 .…”

Decoupling between SARS-CoV-2 transmissibility and population mobility associated with increasing immunity from vaccination and infection in South America

“…Few studies estimated the proportion of infected individuals in South America after the large Gamma and Lambda epidemics in 2021, but some evidence from seroprevalence data support our estimations. A randomized study conducted in Paraguay between March to June 2021 gave a seroprevalence of 23.1% in Asunción and of 26.9% in the central region of the country 30 and a recent seroprevalence survey among adult individuals living in the largest Brazilian city of Sao Paulo also estimate a high proportion (45%: 39-51%) of individuals infected by SARS-CoV-2 31 .…”