In a press conference this past Sunday, President Trump announced that the Food and Drug Administration (FDA) was authorizing the use of convalescent plasma on an emergency basis to treat COVID-19. In the same briefing, the FDA commissioner, Stephen Hahn, claimed that a study found that 35 out of 100 people infected with the virus were saved by this antibody-rich plasma. This remark has caused quite a stir in the scientific community.

Convalescent plasma isn’t a new treatment. It’s been used to fight flu and measles outbreaks before there were vaccines. Recently, it was tried during the Ebola epidemic. It works because when the body encounters a new germ, it makes proteins, or antibodies, which are specially targeted to fight the infection. The antibodies float in plasma, the yellowish, liquid part of blood. This is collected from survivors and given to patients who become newly infected.

Many scientists are saying that the commissioner’s claim wasn’t accurate. According to them, it seems that he confused absolute risk reduction and relative risk reduction. When it comes to data presentation from clinical trials, these are relatively basic concepts. The reason for the mix up was the result of comparing one group of patients who received a particular kind of plasma to another group that got a different concentration at a period of the disease. This shows a relative difference between those specific groups. It doesn’t show what happens between patients that get plasma versus those that don’t. The latter is what’s needed to determine if the treatment is beneficial.

Responding to reproach the following day on Twitter, Hahn wrote, “I have been criticized for remarks I made Sunday night about the benefits of convalescent plasma. 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.”

Besides the FDA commissioner, President Trump and Health and Human Services secretary, Alex Azar also spoke at the press conference and repeatedly focused on the 35% mortality reduction. The president even went so far as to say convalescent plasma is a “powerful therapy” that “had an incredible rate of success.” Many scientists and doctors feel that the proclamations are misleading since the therapy has yet to be tested in clinical trials.

Scientists also point out that the results come from a small subgroup of hospitalized COVID-19 patients that were part of a Mayo Clinic study. This group was under 80 years old, not on ventilators, and received plasma that contained high levels of antibodies within three days of diagnosis. Basing their decision for emergency use off of such limited data seems foolhardy since this doesn’t cover all of the people who get COVID-19. Experts declare that far more data is needed with a much broader set of parameters to see if the results hold up on a wide scale.

Another issue, experts, including those that worked on the study, are trying to figure out is where the 35% number came from. It’s not stated in the official authorization letter from the FDA nor the 17-page memo written by scientists at the agency. It can’t be found anywhere in an analysis of the study conducted by the Mayo Clinic.

All of these discrepancies have left some wondering if the promotion of convalescent plasma was a calculated political move since the day before it was delivered, the president took to Twitter claiming the FDA might be part of the “Deep State” and was making it hard for drug companies to test vaccines and therapeutics. In his tweet, the president tagged Hahn. Yesterday, the FDA denied accusations of there being a political motive behind endorsing the therapy.

Yesterday, the World Health Organization (WHO) spoke out about the recommendations. They reacted to Sunday’s emergency use authorization of convalescent plasma by the FDA. According to the agency, it’s still considered an experimental therapy and needs further testing. Their statement comes after scientists from around the world became worried that widespread use of the treatment in the US will ruin the formal studies that are currently being conducted. Per Dr. Soumya Swaminathan, WHO’s chief scientist, “the results are not conclusive. At the moment, it’s still very low-quality evidence.”