US halts plasma study to treat mild COVID-19 citing 'unlikely benefit'

US halts plasma study to treat mild COVID-19 citing 'unlikely benefit'

The National Institutes of Health announced Tuesday it stopped a clinical trial testing convalescent plasma in mild-to-moderate COVID-19 patients after an independent board found no difference in hospitalizations, deaths or in preventing progression to severe illness.

An independent data and safety monitoring board convened on Feb. 25 to assess trial data, and concluded that while the plasma “caused no harm, it was unlikely to benefit this group of patients,” per a news release.The board recommended to stop enrolling new patients into the study, and this was done “immediately,” according to the release.


“The recent data analysis from the study indicated no significant difference in the proportion of participants who experienced any one of these outcomes [hospitalization, additional care or death within two weeks],” reads the release. “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.”

The study launched in August 2020, and aimed to reach 900 patients across 47 hospital emergency departments (ED) in the U.S., but only enrolled 511 patients. These patients presented to the ED with mild-to-moderate COVID-19 and had at least one underlying condition that would heighten the risk for a severe course of COVID-19 disease, like heart disease or obesity. The patients had symptoms for several days to a week, but weren’t sick enough to require hospitalization.

The concept behind the treatment is that antibodies in the plasma from recovered patients could be infused into ill patients in a bid to improve conditions. Plasma was also used during the 1918 influenza pandemic, the SARS-CoV-1 outbreak in 2003, and the H1N1 influenza pandemic in 2009, the NIH says.


Trial participants received one unit of plasma or a placebo, and researchers studied whether patients went on to require hospital care, sought additional care or died within 15 days of starting the trial. 

The NIH noted over 100,000 people in the U.S. have already been treated with plasma since the beginning of the pandemic, and The American Red Cross is actively seeking plasma donations. Some doctors voiced some cautious optimism over the treatment last spring, though they had uncertainties, specifically whether patients’ improved conditions were due to plasma or another factor.