The head of the US Food and Drug Administration (FDA) walked back his claim that an experimental therapy had provided a dramatic benefit to Covid-19 patients, a rare reversal for an agency that has prided itself on rock-solid science and public trust.
On Sunday night at a press conference with President Donald Trump, FDA Commissioner Stephen Hahn said that blood plasma from Covid-19 survivors given to new patients could save huge numbers of lives.
"What that means isand if the data continues to pan out100 people who are sick with Covid-19, 35 would have been saved because of the administration of plasma," Mr Hahn said.
The FDA chief's remarks followed similar comments by Mr Trumpwho said the therapy is "proven to reduce mortality by 35 per cent"and by Health and Human Services Secretary Alex Azar.
On Monday night, Mr Hahn reversed himself.
"I've been criticised for remarks I made Sunday night concerning the benefits of convalescent plasma. The criticism is entirely justified," Mr Hahn said in a tweet.
He had spent much of Monday taking heat from health experts, including two previous FDA commissioners, for his remarks.
"That was not the way that I would have worded it," said one of the doctors who led the blood plasma study, Professor Arturo Casadevall, chair of the department of molecular microbiology and immunology at the Johns Hopkins School of Public Health. "I hope they will issue a clarification," Prof Casadevall said earlier on Monday.
What the data does show is that a higher dose of blood plasma is better than a lower one. And while there are promising signals that it will lead to a real benefit when compared with a placebo, that is not known yet.
"Until we've a randomised controlled trial, we don't know definitively," Prof Casadevall said.
The administration's misrepresentation of the data may raise fears about how Mr Hahn and the rest of the administration will treat data on a vaccine for the virus.
Mr Trump has said he expects one to be ready in time for his potential re-election, and on Saturday accused unnamed members of the "deep state" at the FDA of slowing work to hurt him politically.
"Deep state" is a term used by Mr Trump to describe employees of government agencies that he believes are manipulating policy to work against his interests. There is no evidence this is happening at the FDA.
The "35 per cent" statistic has several fatal flaws. Since everyone in the programme received blood plasma, it's not known what would have happened compared with patients who did not get the therapy.
And scores of variables, like how sick the patients were and when they were treatedcould have skewed the results.
Mr Robert Califf, the FDA commissioner under the Obama administration, said he thought Mr Hahn had misspoken. "It would be good for Steve to publish a correction," Mr Califf said on Twitter on Monday.
Doctors and patients rely on the FDA to put out authoritative information concerning the safety and efficacy of drugs, vaccines, medical devices and other products, guiding their use not just in the United States but around the world.
The agency has historically carefully guarded its reputation and scientific independence. However, Mr Hahn's comments about 35 out of 100 people being saved were still posted to the FDA's official Twitter account as of Monday afternoon.
BLOOMBERG