A new study by Public Health England (PHE) has shown that one dose of the COVID-19 vaccine reduces household transmission by up to half.Studies have already demonstrated that being vaccinated against coronavirus (COVID-19) significantly reduces your risk of being infected.

This new research shows that those who do become infected 3 weeks after receiving one dose of the Pfizer-BioNTech or AstraZeneca vaccine were between 38% and 49% less likely to pass the virus on to their household contacts than those who were unvaccinated.

Protection was seen from around 14 days after vaccination, with similar levels of protection regardless of age of cases or contacts.

This protection is on top of the reduced risk of a vaccinated person developing symptomatic infection in the first place, which is around 60 to 65% – 4 weeks after one dose of either vaccine.

Households are high-risk settings for transmission and provide early evidence on the impact of vaccines in preventing onward transmission. Similar results could be expected in other settings with similar transmission risks, such as shared accommodations and prisons.

By linking case and household contact data with vaccination status, the study compared the likelihood of transmission for a vaccinated case with an unvaccinated one.

The study included over 57,000 contacts from 24,000 households in which there was a lab-confirmed case that had received a vaccination, compared with nearly 1 million contacts of unvaccinated cases.