On Mar. 2, 2021, the NIH halted a clinical trial evaluating the safety and effectiveness of COVID-19 convalescent plasma in treating emergency department patients who developed mild to moderate symptoms of COVID-19, the disease caused by the coronavirus SARS-CoV-2.

Launched in August 2020, the Clinical Trial of COVID-19 Convalescent Plasma of Outpatients (C3PO was conducted at 47 hospital emergency departments across the U.S. and had enrolled 511 of the 900 participant recruitment goal.