US President Joe Biden has urged unvaccinated Americans to get inoculated against Covid-19, saying that a highly transmissible variant of the virus could cause unnecessary deaths.
“Even while we are making incredible progress, it remains a serious and deadly threat,” Mr Biden said on Friday.
He was speaking at a White House event marking 300 million doses of vaccine administered during the first 150 days of his administration.
“The data is clear: if you are unvaccinated, you’re at risk of getting seriously ill, or dying or spreading it.”
Covid-19 cases have plunged across the country in step with vaccinations, prompting many to resume pre-pandemic activities like indoor dining, sporting events, concerts and travel in recent weeks.
But a large number of Americans – particularly in the politically conservative south – have declined vaccines, despite warnings from health authorities that the virus remains a threat.
"The Delta variant can cause more people to die in areas where people have not been vaccinated," Mr Biden said.
"Some areas will be very hurt."
About 65 per cent of Americans aged 18 and older have had at least one dose, the Centres for Disease Control and Prevention reported, and 142.5 million adults are fully vaccinated.
"Where people have got the two shots, the Delta variant is highly unlikely to result in anything," he said, as "the existing vaccines are very effective".
But at the current pace – about 237,000 first doses administered per day – Mr Biden will fall short of his July 4 goal of having 160 million adults fully vaccinated and 70 per cent with at least one shot.
Vice President Kamala Harris travelled to Georgia on Friday to encourage vaccination. The US should cross the 300 million-shot milestone by Saturday, Mr Biden's 150th full day in office.
Mr Biden’s 70 per cent partial vaccination goal could be met shortly after the Fourth of July, the nation's independence day.
Fifteen states and the District of Columbia have partially vaccinated 70 per cent of adult residents.
The US – which recently announced plans to share its large stockpile of vaccines with needy countries — remains ahead of much of the world in terms of its vaccination programme.
But it also reached a grim milestone in the pandemic this week, as the death toll passed the 600,000 mark, data compiled by Johns Hopkins University showed.
“A few days ago, we crossed 600,000 Americans dead from Covid," Mr Biden said.
"More than every death in World War I, World War II, Vietnam and 9/11 combined. So, even while we’re making incredible progress, it remains a serious and deadly threat."
Public health officials, including CDC chief Dr Rochelle Walensky, have stressed that danger remains, as the Delta variant, first discovered in India, is expected to become the dominant strain in the US.
"As worrisome as this Delta strain is with regard to its hyper-transmissibility, our vaccines work," she said on Friday on the Good Morning America news show.
Studies have shown US-authorised vaccines to be highly effective against the variant, though protection is significantly lower for those with only one dose of a two-shot regimen.
“I would encourage all Americans, get your first shot and when you’re due for your second, get your second shot and you’ll be protected from this Delta variant," Dr Walensky said.