ABSTRACT Background: Understanding SARS-CoV-2 seroprevalence among vulnerable populations is crucial, especially in countries with universal but resource-constrained healthcare systems, such as Brazil. Methods: This was a cross-sectional, population-based household survey within the AVISA study, which aimed to assess seroprevalence among households enrolled in the Family Health Program (ESF). Two serological assays (rapid test and ECLIA) were used to detect anti-SARS-CoV-2 antibodies. Descriptive statistics were calculated and survey-adjusted Poisson regression models with robust variance were estimated, yielding prevalence ratios (PRs) and 95% confidence intervals (CIs). Results: The overall weighted seroprevalence was 35.66% (95% CI: 30.55-40.77) in 2,986 participants. Compared with individuals in the Southeast region, participants in the Northeast and North regions had a 1.48- and 1.38-times higher prevalence of SARS-CoV-2 testing positivity, respectively. Relative to individuals who self-identified as having Black or Brown skin color using IBGE-defined categories, White had a 22% lower prevalence of seropositivity (PR = 0.78, 95% CI 0.63-0.97). Compared to those living in households with four to five family members, individuals living in households with six or more family members had a higher prevalence of seropositivity (PR = 1.34, 95% CI 1.05-1.71). Individuals in the lowest per capita household income quintile were more likely to have SARS-CoV-2 infection (PR = 1.89, 95% CI 1.21-2.95) than those in the highest. Conclusion: This study is the first to assess SARS-CoV-2 seroprevalence among ESF participants, a socioeconomically vulnerable population, served by the primary care public health system. Lower socioeconomic status was associated with higher seroprevalence.
Barros et al. (Thu,) studied this question.