Longitudinal analysis of SARS‐CoV‐2 antibodies in 8000 U.S. first‐time convalescent plasma donations

BACKGROUND: Coronavirus disease 2019 (COVID‐19) convalescent individuals carry antibodies against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) that, through a plasma donation, can be used as a potential therapeutic either in direct transfusion or for the manufacture of hyperimmune globulin (HIG). The success of such interventions depends on the antibody potency in such plasma donations, but little information on the collection of potent units is currently available. STUDY DESIGN AND METHODS: A total of 8749 plasma units, collected from April until September 2020 from first‐time U.S. COVID‐19 convalescent plasma donors, were characterized for SARS‐CoV‐2 immunoglobulin G (IgG) antibodies by Abbott chemiluminescent microparticle immunoassay (CMIA). The period between COVID‐19 onset until donation and donor age, ethnicity, sex, and COVID‐19 severity were evaluated against the obtained signal (index S/C). RESULTS: A marked decrease in mean index S/C was seen over the plasma collection period surveyed, which was significantly correlated to decreases in mean plasma donor age (p < .0001; R(2) = .726) and percentage of donations obtained from COVID‐19 convalescent patients who had been hospitalized (p = .001; R(2) = .4426). The highest titer plasma units were obtained soon after convalescence from COVID‐19 patients who required hospitalization, from advanced age donors, and from Black/African/Hispanic American versus White/Caucasian ethnicities, whereas there was no effect of donor sex on the values obtained with the Abbott CMIA. CONCLUSION: Since the onset of the pandemic, the average SARS‐CoV‐2 IgG values of first‐time U.S. COVID‐19 convalescent plasma donations have significantly dropped, mainly due to donations from progressively younger aged donors who tend to experience less severe COVID‐19.