Convalescent Plasma for Older Adults: A Matter of Titer and Timing?

Passive antibody transfer has repeatedly been suggested as a treatment for COVID-19, but convalescent plasma trials have generally yielded negative results (NEJM JW Infect Dis Jan 2021 and BMJ 2020; 371:m3939; NEJM JW Infect Dis Jan 2021 and N Engl J Med 2020 Nov 24; [e-pub]), and the monoclonal antibody preparations that have received FDA emergency use authorization (but not yet FDA approval) are bamlanivimab and REGN-COV2 (casirivimab + imdevimab). Now, researchers in Argentina have conducted a trial of convalescent plasma involving 160 patients with COVID-19 (aged ≥75, or ≥65 with ≥1 comorbidity; mean overall age, 77; 72% female). Patients were randomized to receive intravenous convalescent plasma (250 mL) or saline within 72 hours of symptom onset. Plasma preparations were derived from 135 donors who had recovered from COVID-19, selected for the highest anti–SARS-CoV-2 spike protein IgG titers (top 28%; all >1:1000 in serum).

Severe respiratory disease occurred in 16% of plasma recipients and 31% of placebo recipients (P<0.03, relative risk reduction, 48%; number needed to treat, 7). If patients who met this endpoint before receiving the intervention were excluded, the risk reduction associated with treatment was 60%. Two and four patients in the plasma and placebo groups, respectively, died (a nonsignificant difference). No adverse events were reported.