Cumulative incidence of SARS-CoV-2 infections among adults in Georgia, USA, August-December 2020.

Chamberlain, Allison T; Toomey, Kathleen E; Bradley, Heather; Hall, Eric W; Fahimi, Mansour; Lopman, Benjamin A; Luisi, Nicole; Sanchez, Travis; Drenzek, Cherie; Shioda, Kayoko; Siegler, Aaron J; Sullivan, Patrick Sean

BACKGROUND Reported COVID-19 cases underestimate true SARS-CoV-2 infections. Data on all infections, including asymptomatic infections, are needed to guide programs. To minimize biases in estimates from reported cases and seroprevalence surveys, we conducted a household-based probability survey in Georgia and estimated cumulative incidence of SARS-CoV-2 infections adjusted for antibody waning. METHODS From August to December 2020, we mailed specimen collection kits (nasal swabs and blood spots) to a random sample of Georgia addresses. One household adult completed a survey and returned specimens for virus and antibody testing. We estimated cumulative incidence of SARS-CoV-2 infections adjusted for waning antibodies, reported fraction, and infection fatality ratio (IFR). Differences in seropositivity among demographic, geographic and clinical subgroups were explored with weighted prevalence ratios (PR). RESULTS Among 1,370 participants, adjusted cumulative incidence of SARS-CoV-2 was 16.1% (95% credible interval (CrI): 13.5-19.2%) as of November 16, 2020. The reported fraction was 26.6% and IFR was 0.78%. Non-Hispanic Black (PR: 2.03, CI 1.0, 4.1) and Hispanic adults (PR: 1.98, CI 0.74, 5.31) were more likely than non-Hispanic White adults to be seropositive. CONCLUSIONS As of mid-November 2020, one in 6 adults in Georgia had been infected with SARS-CoV-2. The COVID-19 epidemic in Georgia is likely substantially underestimated by reported cases.