Washington, Oct 23 (IANS): A Covid-19 vaccine could be available to "all Americans" by early April 2021, US Health and Human Services (HHS) Secretary Alex Azar said.

"By the end of January, enough vaccine for all of our seniors as well as our health care workers and first responders," Xinhua news agency quoted Azar as saying in a CBS News interview on Thursday.

"By the end of March and early April - enough for all Americans," he added.

Azar said the HHS will have enough vaccines authorized by the US 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, had said on Wednesday that all Americans could be immunized with a Covid-19 vaccine by June 2021.

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.

Azar's remarks come as some parts of the US were witnessing a resurgence in the number of fresh coronavirus cases.

Currently the worst-hit country in the world, the US has so far reported a total of 8,404,743 cases and 223,000 deaths.