Vaccination only reduces the risk of infection with the Delta variant of coronavirus by about a third, according to a detailed study of transmission within households.

The research showed that the chance of contracting Delta, which has established itself as the dominant strain of the virus over the past six months, from someone at home was 25 per cent for those double-jabbed, compared with 38 per cent if you were unvaccinated. Even this limited protection begins to wane three months after vaccination, the study led by Imperial College London found.

The scientists found that the risk of onward transmission was little affected by vaccination status of the infected person with peak levels of virus similar in people who had and had not been jabbed.