This “warp speed” approach to vaccine development—a concept that originated with FDA career staff—could be applied to developing other therapeutics. Most of the potentially beneficial treatments are in limited supply, so doctors are forced to ration them. It makes sense to increase clinical trial capacity to include more patients and collect rigorous information on how well these therapies are working.

Take convalescent plasma: Doctors skim antibodies from patients who have recovered from Covid and give them to people who are sick. The theory is that some aspects of the immune response are portable between patients. About 70,000 patients have been dosed with such plasma.

The FDA is granting an emergency-use authorization for plasma, despite concerns last week from public-health leaders at the National Institutes of Health about the limits of the evidence. The decision would have a stronger foundation if patients had participated in a randomized study that looked at whether patients who received plasma fared better than those who didn’t.

To reduce some of the uncertainty, we should expand the NIH Covid trial networks by running more large, practical trials like the U.K.’s Recovery Trial. Recovery, an acronym for Randomised Evaluation of Covid-19 Therapy, randomly assigns patients to experimental treatments using a clear protocol.