Joe Biden received a dose of the coronavirus vaccine on live television in an effort to demonstrate its safety to the American public.
The Pfizer/BioNTech vaccine was administered to the US president-elect at the Christiana Hospital in Newark, Delaware on Monday.
Asked by the nurse practitioner Tabe Mase if he would like her to count to three, Biden was heard to say: "no, no, you just go ahead any time you're ready".
Afterwards, Biden told the journalists watching him: "We owe these folks an awful lot, the scientists and the people who put this together, the frontline workers, the people who were the ones who actually did the clinical work, it's just the amazing.
"I'm doing this to demonstrate that people should be prepared when it's available to take the vaccine.
"There's nothing to worry about, I'm looking forward to the second shot, and so's Jill."
Biden's wife Jill was given the vaccine earlier in the day.
Nearly 320,000 people have died of the coronavirus and nearly 18 million have tested positive in the United States, making it the worst-affected country in the world.
Other senior US politicians including Vice President Mike Pence and Nancy Pelosi, the House speaker, have also received doses.
President Donald Trump, who tested positive for COVID-19 in October, said earlier this month on Twitter that was "not scheduled" to receive the vaccine, but that he expected to do so "at the appropriate time".