Dodd RY, et al. - In order to attract new donors and support the collection of convalescent plasma, routine testing of donations for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies has been implemented and publicized by many blood collection organizations. Researchers here investigated whether testing of donations for SARS-CoV-2 antibodies was linked with alterations in donor characteristics and reactivity of donated blood. Nearly 40% of blood collected by the American Red Cross in the US is from 44 states. On June 15, 2020, testing of all donations was initiated using the Ortho VITROS anti–SARS-CoV-2 S1 Total Ig assay to detect total immunoglobulin. A total of 953,926 donations were tested; of these, 17,336 (1.82%) were reactive; 4,786 (28%) were from first-time donors and 12,550 (72%) from repeat donors for anti–SARS-CoV-2 rates of 2.99% among first-time donors and 1.58% among repeat donors. Findings revealed an increase in the proportion of first-time donors after the introduction of antibody testing, and more frequent detection of reactivity in donations from younger and racial and ethnic minority donors. Further, there was an increase in reactivity rates with time, which may be due to higher rates of prior exposure of donors donating to obtain antibody test results, particularly first-time donors, but may also indicate elevated exposure in the general population or raised recognition of the need for convalescent plasma.