Coronavirus infections in care home residents fell by 62% from five weeks after they received their first vaccine dose, Government-funded research has revealed.
Residents in England who were infected after having the vaccine may also be less likely to transmit the virus, according to preliminary findings from the Vivaldi study.
A national study was launched to find out about COVID-19 infections in care homes, led by Dr Laura Shallcross, and will run until November this year, in collaboration with Four Seasons healthcare and the Department of Health and Social Care. The aim of the study is to find out how many care home staff and residents have been infected with COVID-19, to inform decisions around the best approach to COVID-19 testing in the future.
Researchers tracked in excess of 10,400 care home residents in England, average age being 86, between December and March, comparing the number of infections occurring in vaccinated and unvaccinated groups using data retrieved from routine monthly polymerase chain reaction (PCR) testing.
The study calculated the risk of infection was 56% lower from four weeks after a single dose of either the Pfizer or Oxford-AstraZeneca vaccine, and 62% lower after five weeks.
The “substantial protection” lasted until at least seven weeks after vaccination, which the researchers say “provides some evidence” to support the UK’s decision to extend the dose interval.
Researchers also found samples from positive coronavirus tests taken at least 28 days after a first dose of the vaccine contained less viral material, which suggests a lower level of transmissibility.
Laura Shallcross, from UCL’s 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.
“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.”
The study also found any residents in England who were infected after having the vaccine may also be less likely to transmit the virus.
Chief medical officer for England Professor Chris Whitty said: “These data add to the growing evidence that vaccines are reducing Covid-19 infections and doing so in vulnerable and older populations, where it is most important that we provide as much protection from Covid as possible.”