President Donald Trump has repeatedly predicted that a vaccine for COVID-19 will be available before the Nov. 3 election. But questions from Sen. Mitt Romney on Wednesday revealed that even if that happens, relatively few Americans would receive shots by the end of the year.

And doses still likely would not be available for all Americans until March or April, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Fauci outlined the reasons why during questioning by Romney Wednesday at a hearing of the Senate Health, Education, Labor and Pensions Committee.

Romney noted drugmakers are preparing to manufacture millions of doses of vaccine to be prepared if and when they receive government approval.

“If it [a vaccine] were approved on Nov. 1, what proportion of our population would be able to be vaccinated by, let’s say, the end of the year?” Romney asked. “Is this something that would just go to a small subset of the population or could we possibly inoculate a great majority?”

“Good question, senator,” Fauci said. “It is not going to be a large proportion of the population.”

Fauci explained that the number of doses that the government projects as potentially available is a combined total from many different companies working on separate vaccines. He said they will likely be approved and roll out at different times.

Also, the numbers available by the end of the year will start off relatively small and grow over time.

“In November, there will be maybe 50 million doses available,” Fauci said, if a vaccine were approved by then. “By December, maybe another 100-plus million,” and maybe 700 million by April.

“If you’re talking about who’s going to get vaccinated in December or November, it is not going to be a large proportion of the population,” he said.

Exactly who will receive vaccinations first will be up to an advisory board. But Fauci guessed they will go initially to health care workers and people who are most vulnerable because of underlying health conditions.

Fauci added, “But we’re not going to have all of the doses available, for example, by the end of December. They will be rolling in as the months go by, and maybe by the time you get to the third or fourth month of 2021, then you’ll have doses for everyone.”

The questions came in a hearing where the leaders of the nation’s top health agencies vowed that science, not politics, will guide the approval process for a vaccine.

“We will not delay, but we will not cut corners in our process,” said Stephen Hahn, director of the Food and Drug Administration.

He added, “Decisions to authorize or approve any such vaccine or therapeutic will be made by the dedicated career staff at FDA through our thorough review processes, and science will guide our decisions. … FDA will not permit any pressure from anyone to change that. I will fight for science. ... I will put the interests of the American people before anything else.”