Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), believes that the United States will have at least two hundred million doses of a coronavirus vaccine.

On Tuesday, Dr. Fauci said in an interview with the Journal of the American Medical Association that there are four or five clinical trials underway for vaccine candidates. He said he expects the nation to have millions of doses of a COVID-19 vaccine by early 2021.

“By the beginning of 2021, we hope to have a couple of hundred million doses,” he said.

Dr. Fauci, who is also a key member of the White House Coronavirus Task Force, said Phase III clinical trials for a vaccine candidate developed by Moderna Therapeutics, a US-based biotech company, are expected to start in early July.

The NIAID head said another vaccine candidate from AstraZeneca, which is developed by the University of Oxford, is on a similar track.

“I’m cautiously optimistic that with the multiple candidates that we have with different platforms, that we’re going to have a vaccine that shows a degree of efficacy that would make it deployable,” Dr. Fauci said, adding that most people who get infected with the COVID-19 recover and make a good immune response to clear the virus.

“If the body is capable of making an immune response to clear the virus of natural infection, that’s a pretty good proof of concept to say that you’re going to make an immune response in response to a vaccine,” he said.

However, he warned there is “never a guarantee, ever, that you’re going to get an effective vaccine.”

“It isn’t as if we’re going to make the vaccine, show it’s effective and then have to wait a year to rev up to millions and millions and millions of doses,” Dr. Fauci added. “That’s going to be done as we’re testing the vaccine.”

Several states have started easing restrictions; however, public health authorities say a state of normalcy would widely depend on the availability of a vaccine. Last month, the Trump administration announced a collaboration with AstraZeneca for at least 300 million doses of the vaccine, with a more than $1 billion deal to develop the vaccine.