NIH Halts Trial of Covid-19 Convalescent Plasma in Patients with Mild Symptoms

Colorized scanning electron micrograph of a cell infected with SARS-CoV-2

Photo: NIAID

NIH halted a clinical trial evaluating the safety and efficacy of Covid-19 convalescent plasma in treating emergency department patients who developed mild to moderate Covid symptoms.

Launched in August 2020, the Clinical Trial of Covid Convalescent Plasma of Outpatients (C3PO) was being conducted at 47 hospital emergency departments across the U.S. and had enrolled 511 patients toward its 900-patient enrollment goal. It was studying the effectiveness of using convalescent plasma—blood plasma with antibodies derived from recovered patients—to treat adults.

On Feb. 25, after analyzing interim trial data, an independent data and safety monitoring board (DSMB) determined that while the convalescent plasma intervention caused no harm, it was unlikely to benefit this group of patients. The DSMB then recommended that NHLBI stop enrolling new patients into the study.

Even if enrollment continued, this trial was highly unlikely to demonstrate that Covid-19 convalescent plasma prevents progression from mild to severe illness in at-risk emergency department non-hospitalized participants. More than 100,000 people in the U.S. and many more worldwide have already been treated with it since the pandemic began.