A COVID-19 vaccine could be available to "all Americans" by early April, said U.S. Health and Human Services Secretary (HHS) Alex Azar Thursday.

(File photo: CFP)

"By the end of January, enough vaccine for all of our seniors as well as our health care workers and first responders," Azar said in an interview with CBS. "By the end of March and early April - enough for all Americans."

Azar said HHS will have enough vaccines authorized by the U.S. Food and Drug Administration (FDA) to vaccinate "most vulnerable people" by the end of the year.

Moncef Slaoui, scientific head of Operation Warp Speed, a White House program designed to shorten the amount of time it takes to develop a coronavirus vaccine, said Wednesday all Americans could be immunized with COVID vaccine by June.

He said the pharmaceutical companies Moderna and Pfizer are likely to be the first with vaccine candidates to apply for FDA emergency use authorization, possibly as soon as November or December.

If a vaccine is authorized before the end of the year, Slaoui said approximately 20 to 40 million doses of it will be stockpiled and ready for distribution for a limited population.