As Trump Praises Plasma, Researchers Struggle to Finish Critical Studies

Randomized trials outside the United States have not been able to prove plasma’s effectiveness, either. A trial at seven medical centers in Wuhan, the likely ground zero for the virus, concluded that convalescent plasma did not significantly improve patients’ recovery time.

As in the U.S. trials, the Wuhan study had trouble recruiting participants and concluded early with just 103 volunteers. An analysis recently conducted by researchers, including Drs. Joyner and Casadevall, found that several overseas studies hinted that plasma was effective, but not all of them were randomized.

The Trump administration has framed convalescent plasma as a rare bright spot in the pandemic.

Eager to present his administration as marching toward a “cure,” Mr. Trump has mentioned plasma alongside remdesivir and dexamethasone, two coronavirus treatments that have been shown to be effective in randomized trials.

Dr. Deborah L. Birx, the leader of the White House’s coronavirus task force, at one point pushed for the federal government to secure 500,000 bags of plasma to store for a possible wave of infections in the fall, according to a senior administration official. She also pushed for plasma transfusions in nursing homes, the official said.

When asked about these claims, a task force official said that Dr. Birx wanted to move quickly to capitalize on the period of time after a person is infected, when their plasma contains higher antibody levels. Dr. Birx said she wanted clinical trials to include vulnerable people in nursing homes, the official added.

Dr. Stephen M. Hahn, the F.D.A. commissioner, began discussing the benefits of plasma at White House briefings in March. In interviews and congressional testimony since then, he has presented it as one of the few therapeutics the agency can publicly endorse.

Last week, he said the F.D.A. was “encouraged by the early promising data that we’ve seen” and that it was “studying these data to determine, ultimately, the safety and efficacy of this product.”