Scientists put survivors’ blood plasma to the test

On 13 March, with the COVID-19 pandemic exploding and drugs elusive, Arturo Casadevall published what he considers “maybe the most important paper” of his long career. In The Journal of Clinical Investigation, the infectious disease specialist at Johns Hopkins University and Liise-anne Pirofski of Albert Einstein College of Medicine argued that one effective treatment might already be at hand: the blood plasma of people who have recovered from the disease, rich in antibodies against the virus. The strategy seems to have worked in other infections, the duo pointed out, and the infrastructure for collecting and administering plasma exists. The risks are known and comparatively low. “We recommend that institutions … begin preparations as soon as possible,” they wrote. “Time is of the essence.”

Ten weeks later, more than 16,000 patients at hundreds of U.S. hospitals have received the experimental therapy, and hope that it works could soon give way to evidence. A study of patients treated with serum at Mount Sinai Hospital in New York City, published as a preprint on 22 May, offers hints it may, as do other small studies elsewhere. But randomized controlled clinical trials (RCTs) that will give more definitive answers are still underway.

Blood or plasma from recovered patients has been tried as a therapy since at least the Spanish flu of 1918; reports from that pandemic suggest it helped. It has also been used to fight measles, severe acute respiratory syndrome, and lesser known diseases such as Argentine hemorrhagic fever. In a 1970s study of 188 patients with that disease, only 1% of plasma recipients died, versus 16.5% in a control group. “I think that it has a high likelihood [of working] based on history,” Casadevall says.