Last weekend, FDA chief Stephen Hahn stood with President Trump and extolled the use of plasma as a coronavirus treatment. Trump said convalescent plasma "has proven to reduce mortality by 35%," and Hahn, while qualifying things a bit more, echoed the point. "What that means is—and if the data continue to pan out—100 people who are sick with COVID-19, 35 would have been saved because of the admission of plasma." The problem is that medical experts, even those involved in the very study being cited, couldn't figure out where the 35% figure came from, reports the New York Times. On Monday night, Hahn issued a mea culpa in a Twitter thread. "I have been criticized for remarks I made Sunday night," wrote Hahn. "The criticism is entirely justified. What I should have said better is that the data show a relative risk reduction not an absolute risk reduction."
It may sound like a wonky clarification, but it's a big one, writes Aaron Blake of the Washington Post. Hahn distorted a stat comparing subsets of patients. "Strictly speaking, the treatment would have saved about 3 out of 100 coronavirus patients, not 35," writes Blake. Hahn is taking criticism over the mistake, though the Times quotes a Johns Hopkins researcher involved in the Mayo Clinic study central to the controversy who suggests people shouldn't get too carried away. "Do I know where the 35% comes from?" asks Dr. Arturo Casadevall. "No." But "I think the important thing is that all the indicators show a reduction in mortality." The FDA has granted emergency use authorization for the treatment, and Hahn tweeted that it's not the same as permanent approval. The agency will continue to "monitor its use and will revoke the authorization if needed." (Read more coronavirus stories.)