Those who were infected at least three weeks later were between 38 percent and 49 percent less likely to pass the virus on to people living in the same household, compared with those who had not been vaccinated. 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.
"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," said Peter English, a retired consultant in communicable disease control.
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.
Over 33.8 million people have been given the first jab of the coronavirus vaccine, according to the latest official figures. Meanwhile, a quarter of adults in Britain have been fully vaccinated as Britain's vaccine program has been expanded to include people aged 42 and over.
The number of COVID-related deaths in England and Wales in a week has fallen to the lowest level in six months, new figures from Britain's Office for National Statistics (ONS) showed Tuesday.
A total of 362 deaths registered in England and Wales in the week ending April 16 mentioned COVID-19 on the death certificate, the lowest number since the week ending Oct. 2 last year, according to the ONS.
Experts have warned that despite progress in vaccine rollout, Britain is "still not out of the woods" amid concerns over new variants and the third wave of the pandemic on the European continent.