The research, posted as a pre-print and yet to be peer-reviewed, estimated the effect of both the COVID-19 vaccines on laboratory confirmed symptomatic disease in individuals aged 70 years or older in England.
The researchers, including those from Public Health England (PHE), compared the rate of hospitalisation and deaths in confirmed COVID-19 patients aged over 80 who were vaccinated more than 14 days before testing positive, with unvaccinated cases.
Data suggests that in the over 80s, a single dose of either vaccine is more than 80 per cent effective at preventing hospitalisation, around 3 to 4 weeks after the jab, PHE said in a statement.
Evidence for the Pfizer vaccine suggests that it leads to 83 per cent reduction in deaths from COVID-19, it said.
The data also shows symptomatic infections in over 70s decreased from around three weeks after one dose of both vaccines.
“Vaccination with either a single dose of Pfizer or Oxford-AstraZeneca COVID-19 vaccination was associated with a significant reduction in symptomatic SARS-CoV2 positive cases in older adults with even greater protection against severe disease,” said the authors of the study, adding both the vaccines show similar effects.
They said the protection was maintained for the duration of over six weeks of follow-up, and there is a clear effect of both the vaccines against the UK variant of concern.
Experts say the new analysis adds to growing evidence that the vaccines are working, and are highly effective in protecting people against severe illness, hospitalisation and death.
“This adds to growing evidence showing that the vaccines are working to reduce infections and save lives,” Mary Ramsay, PHE Head of Immunisation, said in the statement.
“While there remains much more data to follow, this is encouraging and we are increasingly confident that vaccines are making a real difference,” Ramsay said.
However, she cautioned that the protection is not complete and it is not known yet how much these vaccines will reduce the risk of someone passing the coronavirus onto others.
“Even if you have been vaccinated, it is really important that you continue to act like you have the virus, practise good hand hygiene and stay at home,” Ramsay added.