Results that show the Oxford-AstraZenenca vaccine may reduce the spread of coronavirus have been hailed as "absolutely superb" by the health secretary.
Matt Hancock said the study shows "vaccines are the way out of this pandemic".
It is the first time a vaccine has been shown to reduce transmission of the virus.
The UK has given a first Covid jab to 9.6 million people so far.
The results of the study, which has not yet been formally published, suggest that the vaccine may have a "substantial" effect on transmission of the virus.
It means the jab could have a greater impact on the pandemic, as each person who is vaccinated will indirectly protect other people too.
Mr Hancock called the study "really encouraging" on Twitter, adding that the results were "absolutely superb".
Speaking on BBC Breakfast, he said this latest analysis showing the vaccine reduces transmission would "help us all get out of this pandemic".