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Convalescent plasma: ‘Flavor of the month’ or valid COVID-19 treatment?


On March 31, soon after the Food and Drug Administration authorized emergency use of antibody-packed plasma from recovered patients with COVID-19, Marisa Leuzzi became the first donor at an American Red Cross center. She hoped it could help her aunt, Renee Bannister, who was failing after 3 weeks on a ventilator at Virtua Hospital in Voorhees, N.J.

It may have worked; 11 days after receiving the plasma, Ms. Bannister was weaned off the ventilator and she is now awake and speaking, said Red Cross spokesperson Stephanie Rendon.

This kind of anecdote is fueling demand for the therapy, which can be provided through an expanded access program led by the Mayo Clinic, backed by the FDA, and the plasma paid for by the U.S. Department of Health & Human Services. But while this program is collecting safety and outcomes data, it’s not a randomized, controlled trial.

Others, however, are pursuing that data. At least a dozen researchers are investigating the potential of plasma – both as a treatment and whether it could act as a stand-in for a vaccine until one is developed.

“One of the things I don’t want this to be is the flavor of the month,” Shmuel Shoham, MD, associate professor of medicine at Johns Hopkins University, said in an interview.

Dr. Shoham, principal investigator for a study evaluating convalescent plasma to prevent the infection in high-risk individuals, said some clinicians, desperate for any treatment, have tried potential therapies such as hydroxychloroquine and remdesivir without evidence of safety or efficacy in COVID-19.

The National Institutes of Health recently said something similar for convalescent plasma, that “there are insufficient clinical data to recommend either for or against” its use for COVID-19.

But plasma has promise, according to a Johns Hopkins School of Medicine’s Bloomberg Distinguished Professor, Arturo Casadevall, MD, PhD, in Baltimore, and Liise-anne Pirofski, MD, a professor at Albert Einstein College of Medicine, New York. They lay out the case for convalescent plasma in an article published online March 13 in the Journal of Clinical Investigation. Passive antibody therapy, they wrote, has been used to stem polio, measles, mumps, and influenza, and more recently has shown some success against SARS-CoV-1 and Middle East respiratory syndrome (MERS).

“The special attraction of this modality of treatment is that, unlike vaccines or newly developed drugs, it could, in principle, be made available very rapidly,” said researchers with the National COVID-19 Convalescent Plasma Project, which includes physicians and scientists from 57 institutions in 46 states. But where principle veers from reality is in availability of the plasma itself, and donors are in short supply.

Aiming to prevent infection

So far, the FDA has approved 12 plasma trials – including Dr. Shoham’s – and the NIH’s lists more than two dozen convalescent plasma studies in the United States and elsewhere.

Most are single-arm trials to determine if one infusion can decrease the need for intubation or help those on a ventilator improve. Two others, one at Johns Hopkins and one at Stanford (Calif.) Hospital are investigating whether convalescent plasma might be used before severe disease sets in.

“A general principle of passive antibody therapy is that it is more effective when used for prophylaxis than for treatment of disease,” Dr. Casadevall and Dr. Pirofski wrote.

Stanford’s randomized, double-blind study will evaluate regular versus convalescent plasma in ED patients who are not sick enough to require hospitalization.

The Johns Hopkins trial, which aims to protect against infection in the first place, will begin at Johns Hopkins, Baltimore, and at Hopkins-affiliated hospitals throughout Maryland, Dr. Shoham said. He hopes it will expand nationwide eventually, and said that they expect to enroll the first patients soon.

To start, the prevention study will enroll only 150 patients, each of whom must have had close contact with someone who has COVID-19 within the previous 120 hours and be asymptomatic. The number of subjects is small, compared with the trial size of other potential therapies, and an issue, Shoham said, “that keeps me up at night.” But finding thousands of enrollees for plasma studies is hard, in part because it’s so difficult to recruit donors.

Participants will receive normal plasma (which will act as a placebo) or convalescent plasma.

The primary endpoint is cumulative incidence of COVID-19, defined as symptoms and a polymerase chain reaction–positive test; participants will be tracked for 90 days. Hospitals and health care workers could then decide if they want to use the therapy, he said.

The study will not answer whether participants will continue to have antibodies beyond the 90 days. Convalescent plasma is given as a rapid response to an emergent pathogen – a short-term boost of immunity rather than a long-term therapeutic.


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