The assertion was breathtaking: Out of 100 people who suffered from the illness caused by the coronavirus, 35 were saved by the injection of antibody-rich plasma from people who had survived the disease. That’s how Food and Drug Administration Commissioner Stephen Hahn described the blood product’s effectiveness on Sunday at a news conference at the White House, when President Trump announced the agency was authorizing use of the plasma on an emergency basis to treat covid-19, the disease caused by the coronavirus.
But the 35-out-of-100 claim wasn’t accurate, scientists said Monday. The FDA commissioner appeared to have mixed up absolute risk and relative risk, which are basic concepts in economics and in the presentation of data from clinical trials. On Monday night, Hahn in a tweet acknowledged he had misspoken during the news briefing about the findings of the convalescent plasma study.
“I have been criticized for remarks I made Sunday night about the benefits of convalescent plasma. The criticism is entirely justified,” Hahn wrote. “What I should have said better is that the data show a relative risk reduction not an absolute risk reduction.”