Severe Acute Respiratory Syndrome Coronavirus 2 Serosurveillance in Blood Donor Populations

(See the Brief Report by Dodd et al, on pages 5–9.) Large-scale population serosurveillance studies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are critical to characterizing the cumulative incidence of SARS-CoV-2 infection and extrapolating the population-level prevalence of presumed immunity. They also help estimate other epidemiological parameters (eg, infection fatality ratios) necessary for mathematical models and guiding pandemic response. Detection of antibodies to the nucleocapsid protein of SARS-CoV-2 (anti-N) reflects a history of natural infection, while detection of antibodies to the spike 1 protein of SARS-CoV-2 (anti-S1) may reflect a history of either natural infection or spike-based vaccination. Unlike passive case surveillance data that are sensitive to heterogeneities in testing uptake and case reporting, a key advantage of large-scale population serosurveillance is the potential to detect evidence of all past infections, including asymptomatic infections. While some countries rapidly established nationally representative SARS-CoV-2 serosurveillance systems [1],...