Background: COVID-19 convalescent plasma (CCP) is an important therapeutic option for outpatients at high risk of hospitalization from SARS-CoV-2 infection. We assessed the safety of outpatient CCP transfusions administered during clinical trials.

Study design and methods: We analyzed data pertaining to transfusion-related reactions from two randomized controlled trials in the U.S. that evaluated the efficacy of CCP versus control plasma in various ambulatory settings. Multivariable logistic regression was used to assess whether CCP was associated with transfusion reactions, after adjusting for potential confounders.

Results: The combined study reported 79/1351 (5.9%) adverse events during the transfusion visit, with the majority 62/1351 (4.6%) characterized by mild, allergic-type findings of urticaria, and/or pruritus consistent with minor allergic transfusion reactions; the other reported events were attributed to the patients' underlying disease, COVID-19, or vasovagal in nature. We found no difference in the likelihood of allergic transfusion reactions between those receiving CCP versus control plasma (adjusted odds ratio [AOR], 0.75; 95% CI, 0.43-1.31). Risk of urticaria and/or pruritus increased with a pre-existing diagnosis of asthma (AOR, 2.33; 95% CI, 1.16-4.67). We did not observe any CCP-attributed antibody disease enhancement in participants with COVID-19 or increased risk of infection. There were no life-threatening severe transfusion reactions and no patients required hospitalization related to transfusion-associated complications.

Discussion: Outpatient plasma administration was safely performed for nearly 1400 participants. CCP is a safe therapeutic option for outpatients at risk of hospitalization from COVID-19.