Instead, Adm. Brett Brett P. Giroir, who heads up national testing efforts, and Alex M. Azar II, the secretary of health and human services, offered a slightly more conservative timetable for vaccine availability.
Both seemed to defend the forecasts made by experts including Dr. Robert Redfield, the head of the Centers for Disease Control and Prevention, who was publicly rebuked by the president for estimating that an effective vaccine may not be widely available to the general public until the middle of next year.
On the CNN program “State of the Union,” Admiral Giroir told the host, Jake Tapper, that “in front of the Senate, Dr. Redfield and I both said that a vaccine that would be widely available in hundreds of millions of doses would not likely happen until mid-2021. That is a fact.”
However, he said, that the president was correct in saying that “We could have as many as a hundred million doses by the end of this year. That is correct.”
“I think everybody is right,” Admiral Giroir said.
Mr. Trump has often promised that the United States would produce a vaccine by Election Day on Nov. 3. But his optimism and projections for widespread availability have been roundly disputed. At the White House on Friday at a news conference, Mr. Trump said that once a vaccine is authorized, “distribution will begin within 24 hours after notice.”
He added: “We will have manufactured at least 100 million vaccine doses before the end of the year. And likely much more than that. Hundreds of millions of doses will be available every month, and we expect to have enough vaccines for every American by April.”
The U.S. population has reached 330 million, according to estimates by the Census Bureau.
Several recent public opinion polls have shown a growing distrust or wariness among Americans of a rushed vaccine. In a new ABC News/Ipsos poll, fewer than 1 in 10 Americans had a great deal of confidence in the president’s ability to confirm vaccine effectiveness; 18 percent reported only a “good amount” of confidence.