An early riser, Keenan received the jab at her local hospital in Coventry, central England, on Tuesday morning at 0631 GMT – a week before turning 91.
Britain began rolling out the COVID-19 vaccine developed by Pfizer and BioNTech on Tuesday, the first Western country to start vaccinating its general population in what was hailed as a decisive watershed in defeating the coronavirus.
The mass inoculation will fuel hope that the world may be turning a corner in the fight against a pandemic that has crushed economies and killed more than 1.5 million, although ultra-cold storage and tricky logistics will limit its use for now.
"I feel so privileged to be the first person vaccinated against Covid-19," said Keenan."It's the best early birthday present I could wish for, because it means I can finally look forward to spending time with my family and friends in the New Year after being on my own for most of the year," she said.