President Joe Biden has said the United States would have enough vaccine for its entire adult population by the end of May, as he announced a deal for pharma giant Merck to produce the shot developed by rival Johnson & Johnson.

“This is the type of collaboration between companies we saw in World War II,” said Biden in announcing the pharmaceutical accord.

“We're now on track to have enough vaccine supply for every adult in America by the end of May,” said the US leader — who previously targeted late July to amass sufficient doses to inoculate all Americans, according to AFP.

“That's progress. Important progress. But it is not enough to have the vaccine supply,” Biden said, stressing that a “wartime effort” still lay ahead to administer the vaccines once acquired.