A single dose of the Pfizer or AstraZeneca vaccine was effective at stopping 62% of coronavirus infections in care homes, a study has found.
The study, conducted by University College London (UCL), found that a single vaccine dose was effective at preventing 56% of infections after four weeks, rising to 62% of infections after five weeks.
The research, funded by the Department of Health and Social Care (DHSC), also suggested that those who caught the virus post-vaccine may be less infectious.
The study analysed coronavirus test-result data for 10,412 long-term residents, all aged over 65, at 310 care homes.
The group had routine monthly PCR tests for the virus as well as further targeted tests if an outbreak was suspected. Of the 36,352 tests carried out between December 2020 and mid-March, 1,335 came back positive for the disease.
By comparing those with the number of cases before vaccination, the researchers estimated both jabs were effective at preventing 56% of infections after four weeks, rising to 62% after five weeks.
Dr Laura Shallcross, consultant in public health medicine at UCL Institute of Health Informatics, said: ‘Our findings show that a single dose has a protective effect that persists from four weeks to at least seven weeks after vaccination.
‘Vaccination reduces the total number of people who get infected, and analysis of lab samples suggests that care home residents who are infected after having the vaccine may also be less likely to transmit the virus.
‘We can also infer that the vaccines protect against the highly transmissible UK variant, as this was prevalent during the study period.’
Around 11% of care home residents included in the study had already been infected with coronavirus in the past.
Researchers said a single dose of either vaccine appeared to have little impact on that group, indicating those with a previous infection were already well-protected.
The team also looked at the Pfizer and Oxford-AstraZeneca vaccines separately and found that the timing and size of the protective effect was similar for both vaccines.
Minister for care, Helen Whately said: ‘The last year has been without a doubt the most challenging in most of our lives.
‘The biggest public health threat in 100 years has ripped families apart and taken far too many, far too soon. But it has also shone a light on the incredible work of our health and care workers, scientists and research teams.
‘Within a year of the pandemic arriving in the UK, we had the first vaccine approved, and just over 100 days later we passed the milestone of vaccinating over half of the adult population. This is a tremendous achievement we should all be proud of.
‘Even more encouraging is the protection the vaccine is providing in practice, including the latest data released this week by University College London as part of their Vivaldi care home study.
‘We know the vaccine is effective in reducing hospitalisation and death but this latest study of elderly care home residents suggests they gain 62% protection from infection within five weeks of just one dose.
‘This is particularly reassuring as we know elderly people living in care homes are the most at risk from this cruel virus. Now over 90% of care home residents have had their first jab and some have had their second jab too, giving them their own defence against the virus.
‘During April we will continue to vaccinate those at risk and around 12m people are in line to receive their second doses. It is absolutely crucial people come forward as soon as they are eligible. When you get the call, get the jab, because the more people who are vaccinated the safer we will all be.’
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