A single shot of either the Oxford-AstraZeneca or the Pfizer-BioNTech Covid jab reduces the chance of needing hospital treatment by more than 80%, an analysis in England shows, APA reports citing BBC.
The Public Health England data showed the effect kicked in three to four weeks after vaccination.
It was based on people over 80 who were the first to receive the jab.
Government scientists hailed the result, saying vaccines would soon take the UK "into a very different world".
More than 20 million people in the UK have had their first dose of a vaccine.
That's over a third of the adult population.
Health Secretary Matt Hancock said the vaccine results were "very strong".
He added: "They may also help to explain why the number of Covid admissions to intensive care units among people over 80 in the UK have dropped to single figures in the last couple of weeks."