Video report by ITV News Political Correspondent Daniel Hewitt
Results that show the Oxford vaccine reduces transmission of Covid have been hailed as the "holy grail" of the pandemic fight.
A single dose of the jab may reduce transmission of coronavirus by 67%, according to a new study - which provides a major boost to the UK’s policy of delaying the second jab for up to 12 weeks.
Before these results, little was known about how effective the Covid-19 vaccines were at preventing transmission of the disease.
Health Secretary Matt Hancock hailed the "encouraging" study's findings as "absolutely superb", adding it "reinforces our confidence that vaccines are capable of reducing transmission and protecting people from this awful disease".
Mr Hancock said the "report shows the Oxford vaccine works and works well", though the data is still pending peer review.
What did the study show?
Researchers found the first dose of the jab offers protection of 76% up to three months.
Results showed the Oxford vaccine may also reduce transmission by 67% – with efficacy rising to 82.4% after the second dose 12 weeks later.
The data from the study by the University of Oxford supports the four to 12-week prime-boost dosing interval that many global regulators, including the UK’s, have recommended.
Experts share their opinions on the study
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.
He told ITV's Good Morning Britain the study "demonstrates that the vaccine protects you and it helps cut the transmission of the disease across the whole community".
"It just shows that the strategy has been right of backing those vaccines"
He added: "The other finding in this report is that the with the 12 week gap between first and second dose, you actually get stronger protection than you do with the shorter gap."
Prime Minister Boris Johnson said the data from the study was “really encouraging”.
On Twitter, he said the "new study today shows the Oxford/AZ vaccine provides significant protection against the virus".
ITV News Science Editor Tom Clarke reports on the study’s findings
"I’m incredibly grateful to all our scientists, NHS staff and volunteers working on our vaccination programme."
Mr Hancock told Sky News: "The really good news embedded in it is that it not just reduces hospitalisations - there were no people in this part of the trial who are hospitalised with Covid after getting the Oxford jab - but also it reduces the number of people who have Covid at all, even asymptomatically, by around two-thirds."
A former chair at the Faculty of Pharmaceutical Medicine, Dr Gillies O’Bryan-Tear, said the results were the first definitive estimate of the impact of vaccination on transmission rates.
“If the effect on transmission is confirmed for the Pfizer vaccine too, this would be very positive,” he said.
“If these vaccines reduce transmission to the extent reported, it will mean that the easing of social restrictions will be enabled sooner, than if we have to wait for herd immunity – which may never in fact be achieved because of insufficient vaccine population coverage.”
He added: “That would be the holy grail of the global vaccine rollout, and these data bring us one step closer.”
The study came as Public Health England (PHE) said it was investigating strains of coronavirus in the UK which have developed a mutation that has been worrying scientists.
Eleven cases in the Bristol area have been identified as the variant that originally arose in Kent but are now showing the E484K mutation.
A cluster of 32 cases in Liverpool also have the same mutation but relate to the original strain of coronavirus that has been around since the start of the pandemic.
The South African variant – which also shows the mutation – is under investigation in at least eight postcode areas of England where cases not linked to travel have been found.
A PHE spokesman said: “PHE is monitoring the situation closely and all necessary public health interventions are being undertaken, including enhanced contact tracing and control measures.”
The E484K mutation has been shown to reduce the effectiveness of vaccines in preventing people contracting Covid-19.
However, public health experts believe current vaccines will still be effective against strains with the mutation, although at a lower level, and are good at preventing severe disease.