Researchers from the US Food and Drug Administration studied 20,000 patients who doctors believed might progress to severe or life-threatening stages of COVID-19, CNN reported.
They received the so-called convalescent plasma between April 3 and June 11 for the study, which was published Thursday in Mayo Clinic Proceedings.
Less than 1 percent of them experienced serious adverse events and the number of those who died dropped to 8.6 percent at the seventh day of the trial, compared to the 12 percent who died in a previous part of the safety study of 5,000 patients, according to CNN
“Our efforts to understand convalescent plasma continue,” Dr. Michael Joyner, a principal investigator at Mayo Clinic and study author, wrote on the clinic website. “We’re optimistic, but must remain objective as we assess increasing amounts of data.”
The treatment – which has been used to treat measles, influenza and Ebola – takes advantage of the fact that people who recover from an infection develop virus-fighting antibodies in their blood.
Transfusions of their convalescent plasma — the clear liquid after blood cells are removed — may provide the immune systems of recipients a boost in fighting off the virus.
The new study is the largest analysis yet of the experimental treatment that physicians resorted to during a grass-roots effort in the early weeks of the outbreak, the Washington Post reported.
“The actionable message here is that this is safe, inexpensive and the mortality rates in sick patients are quite low,” said Joyner, an anesthesiologist, the newspaper reported.
He noted, however, that there is a “chicken and egg” dilemma in trying to conclusively determine the treatment’s effectiveness because the patients were given it through an expanded access program created by the FDA, not in a clinical trial in which patients are randomly assigned to receive the treatment or a placebo, the Washington Post reported.
Researchers speculated that the death rate may have dropped because plasma has become more widely available and was given earlier in the illness, which is when it is more likely to be effective, according to the paper.
But the drop in mortality could also be due to improved care as the outbreak progressed — or less severely ill people may have begun to show up at hospitals and received the treatment.
“You’d like to have the gold standard [of evidence] in something this important, and I feel like it always ends up here with this approach,” said Dr. Jeffrey Henderson, an infectious-disease specialist at Washington University in St. Louis who has been researching the use of plasma.
“It’s pushed into action quickly, because there’s no other option, and there’s a theoretical reason in the moment that it works,” he told the Washington Post.