Half of the adult population in the US has been fully vaccinated against Covid-19, according to federal data released on Tuesday, marking a major milestone in the country's efforts to beat the virus.
More than 163 million people have received at least one dose of the vaccine and of that number, 129 million have been fully vaccinated.
Everyone over the age of 12 is eligible to be vaccinated in the US, which has a total population of about 330 million.
The Centres for Disease Control and Prevention (CDC) defines fully vaccinated people as those who have reached the two-week mark after their final dose of the two-shot Pfizer or Moderna regimen or the single-dose Johnson & Johnson vaccine.
President Joe Biden has set the goal of having 70 per cent of the US adult population receive at least one dose of vaccine by July 4, the nation's independence day. The CDC says that currently, 61.8 per cent of adults have had at least one dose of vaccine.
States across the country have been using several methods to encourage people to be immunised, including cash lottery entries, sporting event tickets and free food.
The White House says there is now at least one vaccination location within eight kilometres of 90 per cent of the US population.
Coronavirus cases and hospital admissions as well as deaths are on the decline nationwide, making for low numbers not seen since last spring.
The CDC has reported a seven-day average case count of less than 23,000 per day as well as an average of 457 daily deaths.
"I remain cautious but hopeful they will continue to trend downward," CDC chief Dr Rochelle Walensky said.
A new CDC study, published on Tuesday, discussed the efficacy of Covid-19 vaccines.
Researchers tracked 101 million fully vaccinated people in the US from January to April and found that there were 10,300 "breakthrough cases" reported – one infection for every 10,000 fully vaccinated people.
Of those cases, 25 per cent were admitted to hospital and 2 per cent died.
"Even though [Food and Drug Administration]-authorised vaccines are highly effective, breakthrough cases are expected, especially before population immunity reaches sufficient levels to further decrease transmission," the report said.
The nation's vaccine programme is allowing for further flexibility in business and school reopenings as well as for global travel. Schools in Los Angeles and New York City, among the nation's largest educational systems, said they will reopen in-person classes in the autumn.
On Monday, the UAE embassy in Washington said travellers from the US would be allowed to enter the Emirates without requiring a quarantine, though a negative Covid-19 test will still be required.
The US has recorded over 590,000 deaths from Covid-19, according to Johns Hopkins University, and has reported more than 33 million cases.
