Scientists were immediately skeptical when Food and Drug Administration chief Stephen Hahn, Health Secretary Alex Azar, and President Trump announced Sunday evening that the FDA had given emergency use approval for plasma from recovered COVID-19 patients, right before the Republican National Convention. And they were baffled when all three men claimed plasma had been shown to reduce deaths by 35 percent, meaning, Hanh said, that 35 out of 100 COVID-19 patients "would have been saved because of the administration of plasma."
That impressive statistic was evidently excavated from a small subsample of a large observational study from the Mayo Clinic, and it doesn't mean what Trump, Azar, and Hahn said it does. Hahn and whoever else came up with the number "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," The Washington Post notes, explaining:
Essentially, the Trump administration figures had compared one group of patients who got a certain kind of plasma with a group who got a different concentration at a different point in the disease, thus showing the relative difference between those groups. It was not a measure of what happens when some patients get plasma and some don't — the kind of research necessary to send a signal of whether a treatment is truly helping. The FDA also considered data from other studies. [The Washington Post]
After facing criticism from incredulous medical scientists, Hanh acknowledged his error:
Scientists have reasonable hopes that convalescent plasma, a century-old treatment, will be effective at helping COVID-19 patients recover, at least until a reliable treatment is found or developed. But so far the evidence is "still very low-quality" and "not conclusive, World Health Organization chief scientist Dr. Soumya Swaminathan cautioned Monday.
It isn't really the exaggeration of plasma's benefits that worry medical experts, The New York Times reports. It's that, given how "Trump has appeared to politicize the process of approving treatments and vaccines for the coronavirus," nobody will believe "the scientific judgment of the FDA" when it says a vaccine is safe and effective.