Factors related to the development of high antibody titres against SARS‐CoV‐2 in convalescent plasma donors from the ConPlas‐19 trial

Abstract

Background and ObjectivesThe efficacy of COVID‐19 convalescent plasma (CP) associates with high titres of antibodies. ConPlas‐19 clinical trial showed that CP reduces the risk of progression to severe COVID‐19 at 28 days. Here, we aim to study ConPlas‐19 donors and characteristics that associate with high anti‐SARS‐CoV‐2 antibody levels.Materials and MethodsFour‐hundred donors were enrolled in ConPlas‐19. The presence and titres of anti‐SARS‐CoV‐2 antibodies were evaluated by EUROIMMUN anti‐SARS‐CoV‐2 S1 IgG ELISA.ResultsA majority of 80.3% of ConPlas‐19 donor candidates had positive EUROIMMUN test results (ratio ≥1.1), and of these, 51.4% had high antibody titres (ratio ≥3.5). Antibody levels decline over time, but nevertheless, out of 37 donors tested for an intended second CP donation, over 90% were still EUROIMMUN positive, and nearly 75% of those with high titres maintained high titres in the second sample. Donors with a greater probability of developing high titres of anti‐SARS‐CoV‐2 antibodies include those older than 40 years of age (RR 2.06; 95% CI 1.24–3.42), with more than 7 days of COVID‐19 symptoms (RR 1.89; 95% CI 1.05–3.43) and collected within 4 months from infection (RR 2.61; 95% CI 1.16–5.90). Male donors had a trend towards higher titres compared with women (RR 1.67; 95% CI 0.91–3.06).ConclusionSARS‐CoV‐2 CP candidate donors' age, duration of COVID‐19 symptoms and time from infection to donation associate with the collection of CP with high antibody levels. Beyond COVID‐19, these data are relevant to inform decisions to optimize the CP donor selection process in potential future outbreaks.