It was the first time that Mr. Trump tacitly acknowledged another appearance problem — that he has received the kind of intensive and costly medical care for coronavirus that is not available to any member of the general public.
In an interview on Wednesday, Dr. George Yancopoulos, Regeneron’s president and chief scientific officer, said it was possible that Mr. Trump responded to the treatment and that the level of virus had declined. “That’s a logical conclusion,” Dr. Yancopoulos said. “Based on his symptomology, that has to have happened.”
But neither Dr. Yancopoulos nor Mr. Trump can definitively say whether the treatment worked because any drug must be proved in large clinical trials that compare the outcomes of people who got the product with those who received a placebo. Those trials have not yet been completed.
Dr. Peter Chin-Hong, an infectious disease specialist at U.C.S.F. Health in San Francisco, said in his opinion, there was “one million percent no” chance that the Regeneron treatment could have cured Mr. Trump in 24 hours, as the president claimed.
Another explanation, he said, is that the president is experiencing the effects of the steroid dexamethasone, which he has been receiving since Saturday, which is known to reduce fever and can create feelings of well-being and euphoria in patients. “This is all in keeping with the dexamethasone speaking,” Dr. Chin-Hong said.
The president has been desperate to announce some kind of definitive treatment, or a vaccine, ahead of the election on Nov. 3, in which nearly all polls show him trailing former Vice President Joseph R. Biden Jr., the Democratic nominee, nationally and in key states.
Mr. Trump has also been looking for a type of miracle cure for the virus for months, initially seizing on hydroxychloroquine as an answer before health experts raised concerns about its use. But his disdain for those experts has been consistent with his general refusal to believe in science, a refusal that led The New England Journal of Medicine, in an editorial published on Wednesday, to say the Trump administration had responded so poorly to the coronavirus pandemic that it had “taken a crisis and turned it into a tragedy.”