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 around 40% 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.