President Joe Biden said Thursday that federal authorities have purchased additional doses of Pfizer’s and Moderna’s COVID-19 vaccines, putting the government on track to have enough supply for 300 million Americans by summertime. Biden made the remarks at the National Institutes of Health (NIH) in Bethesda, Maryland, on Thursday, where he spoke about the nation’s vaccine stockpile, a fraught topic amid reports that demand is far outstripping supply. “Just this afternoon, we signed a final contract for 100 million more Moderna and 100 million more Pfizer vaccines,” with an expected delivery date around the end of July, Biden said. Both companies also agreed to expedite delivery of 100 million doses by the end of May, about a month ahead of schedule. “That’s a month faster. That means lives will be saved. That means we’re now on track to have enough supply for 300 million Americans by the end of July,” …