Britain has begun vaccinating its population with the COVID-19 shot developed by Oxford University and AstraZeneca, hailing it as a scientific triumph.
The UK is rushing to vaccinate its population amid an acute health crisis from the pandemic.
More than 75,000 people in the UK have died from COVID and cases are rising sharply, fuelled by a separate variant of the virus.
Just under a month since the UK became the first country in the world to roll out the vaccine developed by Pfizer and Germany's BioNTech, it is now adding the AstraZeneca shot to its arsenal to fight the virus.
Dialysis patient Brian Pinker, 82, was first to get the jab.
"I am so pleased to be getting the COVID vaccine today and really proud that it is one that was invented in Oxford," he said. Pinker, a retired maintenance manager has been having dialysis for kidney disease just a few hundred metres from where the vaccine was developed.
The UK has now put more than a million COVID-19 vaccine doses into arms - more than the rest of Europe put together, Health Secretary Matt Hancock said.
"That's a triumph of British science that we've managed to get where we are," Hancock told Sky. "Right at the start, we saw that the vaccine was the only way out long term."
Prime Minister Boris Johnson's government has secured 100 million doses of the Oxford/AstraZeneca vaccine which can be stored at fridge temperatures between two to eight degrees, making it much easier to distribute than the Pfizer shot.
Six hospitals in England are administering the first of around 530,000 doses Britain has ready. The program will be expanded to hundreds of other British sites in coming days, and the government hopes it will deliver tens of millions of doses within months.
The US Centres for Disease Control and Prevention said it had administered 4.2 million first doses of COVID-19 vaccines as of Saturday and distributed 13.07 million doses.
But Israel is the world leader: more than a tenth of its population have had a vaccine and Israel is now administering more than 150,000 doses a day.
Other Western countries have taken a longer and more cautious approach to rolling out vaccines, though Russia and China have been inoculating their citizens for months with several different vaccines still undergoing late-stage trials.
India approved the Oxford/AstraZeneca vaccine on Sunday for emergency use.
One dose of caution was introduced by ITV political editor Robert Peston who said scientists are not fully confident that COVID-19 vaccines will work on a new variant of the coronavirus found in South Africa.
The spread of the variant virus has also forced the government to change its approach to vaccination. Britain is now prioritising getting a first dose of a vaccine to as many people as possible over giving second doses. Delaying the distribution of second shots should help stretch the supply.
Andrew Pollard, the head of the Oxford Vaccine Group and chief investigator into the trial of the shot, also received the vaccine.
"This is a really critical moment. We are at the point of being overwhelmed by this disease," he told BBC TV. "I think it gives us a bit of hope, but I think we've got some tough weeks ahead."