U.S. President Joe Biden announced Tuesday that there would be enough doses of the coronavirus vaccine available for the entire adult population in the United States by the end of May, although he said it would take longer to actually inoculate everyone, and he urged people to remain vigilant by wearing masks.

Biden had previously said there would be enough doses by the end of July. On Tuesday, he said the faster production of the vaccine was in part the result of an agreement by pharmaceutical giant Merck & Co. to help manufacture the new Johnson & Johnson coronavirus vaccine under an unusual deal brokered by the White House.

He said that agreement, along with other efforts by the government to help Johnson & Johnson produce more doses quickly, would substantially increase the supply of the new vaccine and ramp up the pace of vaccination just as worrisome new variants of the virus have been found in the United States.