Trump’s order authorizes plasma treatment for COVID-19.

WASHINGTON — President Donald Trump on Sunday announced emergency authorization to treat COVID-19 patients with convalescent plasma — a move he called “a breakthrough,” one of his top health officials called “promising” and other health experts said needs more study before it’s celebrated.

The announcement came after White House officials complained there were politically motivated delays by the Food and Drug Administration in approving a vaccine and therapeutics for the disease.

Trump put himself at the center of the FDA’s announcement of the authorization at a news conference Sunday evening. The authorization makes it easier for some patients to obtain the treatment but is not the same as full FDA approval.

The blood plasma, taken from patients who have recovered from the coronavirus and rich in antibodies, may provide benefits to those battling the disease. But the evidence so far has not been conclusive about whether it works.

In a letter describing the emergency authorization, the chief scientist for the FDA, Denise Hinton, said: “COVID-19 convalescent plasma should not be considered a new standard of care for the treatment of patients with COVID-19” and added “additional data will be forthcoming.”

But the timing allowed Trump to head into his convention with momentum. He and aides billed it as a “major” development. During Sunday’s 18-minute press conference, Trump said he thought there had been a “logjam” at the FDA over granting the emergency authorization. He alleged there are people at the FDA “that can see things being held up . . . and that’s for political reasons.”