More than half of all American adults have been vaccinated against COVID-19, the White House said, roughly six weeks before US President Biden's July 4 goal of a 70 percent inoculation rate.
The halfway mark comes as federal, state and local leaders press ahead with delivering COVID-19 shots to people who have not yet received them, while also battling vaccination hesitancy, fears and misinformation.
"Now, with another week left in May, half of all US adults are fully vaccinated," White House senior COVID-19 adviser Andy Slavitt tweeted overnight.
Biden's White House COVID-19 Task Force has scheduled a news briefing for Tuesday afternoon.
New coronavirus infections nationwide have settled into a sustained decline as more people become vaccinated.
The number of new US infections fell to a seven-day average of 22,877 on Sunday, the lowest since June and less than one-tenth of its post-holiday peak of more than 250,000, according to Centers for Disease Control and Prevention data.
People as young as 12 can also now receive the Pfizer-BioNTech COVID shot, while Moderna said on Tuesday its vaccine was also effective in adolescents, opening the door to a possible second US-approved vaccine for youth later this year.
A growing number of localities have announced further reopening efforts as the United States heads into its unofficial summer kick-off with the Memorial Day holiday this weekend.
US travel is on the rise and, while masks are still required for interstate public transportation, many local mandates have been lifted.