The Pfizer-BioNTech and Oxford-AstraZeneca vaccines have been "highly effective" in reducing coronavirus infections and severe illness among elderly people in Britain, official data showed on Monday.
In those aged over 80, a single dose of either vaccine is more than 80 per cent effective at preventing the need for a hospital stay about three to four weeks after the jab.
The figures came from a Public Health England real-world study from data gathered since January.
France and Germany are considering reversing their refusal to authorise the AstraZeneca vaccine for people over 65 after concerns of its efficacy.
British Health Secretary Matt Hancock praised the new study as "extremely good news".
"The detailed data show that the protection you get from catching Covid 35 days after a first jab is even slightly better for the Oxford jab than for Pfizer," Mr Hancock said.
Both vaccines "are highly effective in reducing Covid-19 infections among people aged 70 years and over", the study said.
The Pfizer-BioNTech vaccine offers protection against catching the disease of between 57 and 61 per cent after the first dose, with the AstraZeneca vaccine offering between 60 and 73 per cent, the study said.
"This adds to growing evidence showing that the vaccines are working to reduce infections and save lives," said Mary Ramsay, Public Health England's head of immunisation.
"It is important to remember that protection is not complete and we don't yet know how much these vaccines will reduce the risk of you passing Covid-19 on to others."
Britain has given the first dose of one of the two vaccines to more than 20 million people as part of a mass campaign that is seen as crucial in taming one of the world's worst outbreaks, which has claimed almost 123,000 lives.
Prof Jonathan Van-Tam, deputy chief medical officer for England, said the results "vindicated" Britain's approach.
"I think in time the data emerging from the programme will speak for itself and other countries will doubtless be very interested in it," Prof Van-Tam said.
Britain announced another 104 deaths on Monday, and 5,455 new cases, almost half of the number recorded last Monday.
The number of Covid admissions to intensive care units among people aged over 80 has dropped to single figures in the past two weeks, Mr Hancock said.
Britain will next week begin to unwind its third lockdown, with a plan for life to return to normal by the end of June.
The latest results highlighted the importance of everyone getting vaccinated, Prof Van-Tam said.
"It shows us, gives us those first glimpses, of how if we are patient and we give this vaccine programme time to have its full effect, it is going to hopefully take us into a very different world, in the next few months."