Researchers said that the first dose of the Oxford/AstraZeneca jab offers protection of 76 per cent for up to three months and may reduce transmission by 67 per cent – with efficacy rising to 82.4 per cent after the second dose 12 weeks later.
The data from the study by the University of Oxford, which has not yet been peer reviewed, supports the four to 12-week prime-boost dosing interval that many global regulators, including the UK’s, have recommended.
Before these results, little was known about how effective the Covid-19 vaccines were at preventing transmission of the disease.
The findings indicate that those who have been vaccinated are not only protected from the disease, but that they are not likely to pass on the virus to anyone.
It also suggests the vaccine eliminates severe illness, as none of those in the study were admitted to hospital with coronavirus.
Health Secretary Matt Hancock said: “This is a hugely encouraging study and further reinforces our confidence that vaccines are capable of reducing transmission and protecting people from this awful disease.
“This report shows the Oxford vaccine works and works well.”
Prime Minister Boris Johnson said the data from the study was “really encouraging”.
As of Monday 9,646,715 people had received their first does of a vaccine.