Progression and Predictors of SARS-CoV-2 Antibody Seroreactivity In US Blood Donors

The second largest US blood center began testing for antibodies to SARS-CoV-2, the etiologic agent of Coronavirus Disease-2019 (COVID-19) to identify potential COVID-19 Convalescent Plasma (CCP) donors and encourage blood donation. We report the non-vaccine seroprevalence of total immunoglobulin directed against the S1 spike protein of SARS-CoV-2 in our donors. Unique non-CCP donor sera from June 01to December 31, 2020 were tested with the Ortho VITROS Anti-SARS-CoV-2 total immunoglobulin assay (reactive: signal-to-cutoff (S/C) ≥ 1). Multivariate regressions including age, sex, race-ethnicity, ABO, RhD, highest education level, donor experience, regional collection center and drive type factors were conducted to identify demographics associated with the presence of antibodies and with S/C values. Unique donors (n = 523,068) showed an overall seroprevalence of 6.12% over 7 months, with the highest prevalence in December 2020 around Lubbock, TX (24.3%). In a subset of donors with demographic information (n = 394,470), lower odds of antibody reactivity were associated with female sex, non-Hispanic White or Asian race/ethnicity, age ≥ 65, graduate education, blood Group O, and history of blood donation. In reactive donors (n = 24,028), antibody signal was associated with male sex, race/ethnicity other than non-Hispanic White, low educational attainment, age 16-17 years and geographic location. Seroprevalence continues to grow in US blood donors but varies significantly by region. Temporal trends in reactivity may be useful to estimate effectiveness of public health measures. Before generalizing these data from healthy donors to the general population, rates must be corrected for false-positive test results and adjusted to match the wider US demography.