Abstract

Comprehensive data on transmission mitigation behaviors and SARS-CoV-2 infection and serostatus are needed from large, community-based cohorts to identify SARS-CoV-2 risk factors and impact of public health measures. From July 2020 to March 2021, ≈5,500 adults from the East Bay Area, California were followed over three data collection rounds. We estimated the prevalence of antibodies from SARS-CoV-2 infection and COVID-19 vaccination, and self-reported COVID-19 test positivity. Population-adjusted SARS-CoV-2 seroprevalence was low, increasing from 1.03% (95% CI: 0.50-1.96) in Round 1 (July-September 2020), to 1.37% (95% CI: 0.75-2.39) in Round 2 (October-December 2020), to 2.18% (95% CI: 1.48-3.17) in Round 3 (February-March 2021). Population-adjusted seroprevalence of COVID-19 vaccination was 21.64% (95% CI: 19.20-24.34) in Round 3. Despite >99% of participants reporting wearing masks, non-Whites, lower-income, and lower-educated individuals had the highest SARS-CoV-2 seroprevalence and lowest vaccination sero