A single dose of a COVID-19 vaccine can cut transmission of coronavirus by up to half, a Public Health England (PHE) study showed on 28 April.

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Those who were infected at least three weeks later were between 38 per cent and 49 per cent less likely to pass the virus on to people living in the same household, compared with those who had not been vaccinated, according to the study, Xinhua reported. People included in the research were those who have had a single dose of either the Pfizer or AstraZeneca vaccines, the first two authorized for use in Britain. Peter English, a retired consultant in communicable disease control, told Sky News that the findings are "extremely encouraging".

"The evidence was already mounting that vaccination will prevent people from becoming infected. This study shows that even if people who are vaccinated do become infected, they are considerably less likely to be infectious, and to pass the infection on to others", he said. "This is an extremely encouraging set of findings", he added. The study, which has yet to be peer-reviewed, included more than 57,000 people living in 24,000 households related to a vaccinated person. They were compared with nearly 1 million contacts of people who had not been vaccinated. More than 33.8 million people have been given the first coronavirus vaccine jab, according to the latest official figures. Meanwhile, a quarter of adults in Britain have been fully vaccinated as the country's vaccination program has been expanded to include people aged 42 and over.