The Pfizer and AstraZeneca vaccines are more than 80% effective at preventing hospitalisations from Covid-19 in those over 80 after one dose of either shot, Public Health England (PHE) said on Monday, citing a pre-print study
PHE said the real world study also found that protection against symptomatic Covid in those over 70 ranged between 57-61% for one dose of Pfizer-BioNTech's vaccine and between 60-73% for the Oxford-AstraZeneca one four weeks after the first shot.
"These results 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," British health minister Matt Hancock told a news conference. "This is seriously encouraging."
Britain has now administered a first dose of Covid-19 vaccine to more than 20 million people, or just over 30% of the population, with the elderly getting priority.
PHE submitted its analysis for peer-review after providing initial findings of the real-world impact of the rollout a week ago. A separate study in healthcare workers has shown one dose of a vaccine can reduce by 70% the number of people catching asymptomatic Covid-19.
The health authority said evidence suggested that the Pfizer vaccine causes an 83% reduction in Covid-19 deaths among the over-80s. There was no equivalent data for the AstraZeneca vaccine, which began to be administered at a later date.
PHE Head of Immunisations Mary Ramsay said that while more work needed to be done to understand the impact of vaccines in reducing transmission of the coronavirus, the effect of the rollout was already apparent.
"This adds to growing evidence showing that the vaccines are working to reduce infections and save lives," she said.
Another PHE official said more work was needed to establish the efficacy of vaccines against the so-called Brazilian variant of the coronavirus.
Britain's use of the AstraZeneca vaccine on elderly people contrasts with many European countries, which have cited a lack of clinical trial data for their decision not to roll it out to older cohorts.
Asked whether the data justified Britain's approach, England's deputy Chief Medical Officer Jonathan Van Tam said it was "not immunologically plausible" that the vaccine would work in younger people and not older people.
"We took the view that it almost certainly would work," he said. "The PHE data have clearly vindicated that approach today."