President Joe Biden said Tuesday the United States would have sufficient vaccine supply by the end of May to inoculate the entire US adult population.

"We're now on track to have enough vaccine supply for every adult in America by the end of May," said Biden -- who had previously forecast it would take until the end of July to amass that many doses.

"That's progress. Important progress. But it is not enough to have the vaccine supply," Biden said, stressing the work still ahead to administer the vaccines once acquired.

"We need vaccinators, people who put the shots in people's arms, millions of Americans' arms."

"Great news, but stay vigilant," Biden said. "It's not over yet."

President Joe Biden said the United States would have sufficient vaccine supply by the end of May to inoculate its US adult population
President Joe Biden said the United States would have sufficient vaccine supply by the end of May to inoculate its US adult population AFP / JIM WATSON

Biden made the announcement during a short speech in which he confirmed a deal for pharma giant Merck to produce rival Johnson & Johnson's single-dose Covid-19 vaccine to boost supply nationwide.

"This is the type of collaboration between companies we saw in World War II," Biden said.

The US leader said that Johnson & Johnson's vaccine manufacturing facilities "will now begin to operate 24/7."

The J&J vaccine is the third to receive US regulatory approval for emergency use.

Unlike the two-dose Pfizer and Moderna vaccines, the J&J vaccine requires just one dose, and is stored at fridge temperatures, offering logistical and practical advantages.

Johnson & Johnson has so far said it aims to deliver 100 million doses to the United States by June.

Coronavirus