Brian Pinker, an 82-year-old dialysis patient, was the first person to receive the vaccine at a hospital a few hundred meters away from where it was developed.
"I am so pleased to be getting the vaccine today and I'm really proud that it is one that was invented in Oxford," he said. "The nurses, doctors and staff today have all been brilliant and I can now really look forward to celebrating my 48th wedding anniversary with my wife Shirley later this year."
A 'pivotal' moment
As many as half a million doses are ready to be administered over the next 24 hours, the British government said.
The vaccine costs just 3 pounds ($4.10, €3.35) per shot.
It also can be stored in regular refrigerators, making it easier for GPs and healthcare workers to distribute.
British Health Secretary Matt Hancock said in an interview with broadcaster Sky News on Monday that it was "a triumph for British science" and "a pivotal moment" in fighting COVID-19.
Germany's BioNTech, along with its US partner Pfizer, was the first company in the world to develop an effective vaccine against the virus.
But it is five times more expensive and must be kept at -70 degrees Celsius (-112°F).