Case series studying convalescent plasma use in the treatment of COVID-19 have been promising, but additional, high-quality studies are needed to determine the efficacy of the treatment when applied for prophylaxis, for early phases of illness, and for severe illness. Previous studies of convalescent plasma in treating other viral diseases have identified factors to consider when designing treatment protocols, including timing of administration relative to onset of illness, timing of donation relative to resolution of symptoms, severity of illness of the donor, pretransfusion serology of the recipient, and antibody titers of the donor. There are many clinical trials studying treatment of, and prophylaxis against, COVID-19 using convalescent plasma. In addition to clinical trials, the FDA also allows treatment through two other pathways: the "Expanded Access to Convalescent Plasma for the Treatment of Patients with COVID-19" protocol, and emergency investigational new drug applications. The FDA also provides criteria for donation of convalescent plasma.
Convalescent plasma to treat coronavirus disease 2019 (COVID-19): considerations for clinical trial design