The Oxford vaccine is up to 90% effective in preventing COVID-19, according to tests on thousands of volunteers.
The result compares with the Pfizer and Moderna vaccines, which were recently shown to be 95% and 94.5% effective respectively.
The vaccine, codenamed AZD1222, was developed at Oxford University with support from the pharmaceutical giant AstraZeneca.
“We have a vaccine for the world,” Professor Andrew Pollard, chief investigator of the Oxford Vaccine Trial at Oxford, said.
He added: “It’s a really exciting day.”
For one course of dosing – where people were given a half dose of AZD1222, followed by a full measure at least a month after – there was an efficacy rate of 90%.
When two full doses were given at least a month apart, the Oxford inoculation had an efficacy of 62%.
A total of 2,741 people were on the course that proved 90% effective, while 8,895 were given two full doses.
When all the results are tabulated, the average efficacy of the vaccine works out to 70%.
Professor Pollard went on: “We think that by giving smaller first dose we are setting up the immune response better to respond. We will dig in more to that. We have started work this morning.”
He added: “It’s critical to understand what everyone is measuring. What counts as COVID disease varies between different protocols.
“If you are only counting hospitalisations then we would have bigger efficacy. We count mild disease and that is much harder to protect against.”
The results will be submitted to a scientific journal for peer review within 24 hours.
Speaking to Kay Burley this morning, Health Secretary Matt Hancock said: “This is really encouraging news of the Oxford-AstraZeneca vaccine that obviously we’ve been backing since the start.
“I’m really very pleased, I really welcome these figures.”
Mr Hancock added that he was expecting the information to be sent to the regulator to make sure it is safe.
He added: “We’ve got 100 million doses on order and should all that go well, the bulk of the rollout will be in the new year.
“So having two vaccines that appear to have effectiveness, done right, in the 90% range is really really good news. Fantastic news.”
According to Professor Sarah Gilbert from Oxford, there was a reduction in transmission following administration of the inoculation.
She said: “We are seeing reduction in asymptomatic infections.
“It looks like the vaccine is protecting against severe disease and mild disease – that it is going to make a big difference to transmission. It is good news all round.”
Prime Minister Boris Johnson tweeted: “Incredibly exciting news the Oxford vaccine has proved so effective in trials. There are still further safety checks ahead, but these are fantastic results.
“Well done to our brilliant scientists at @UniofOxford & @AstraZeneca, and all who volunteered in the trials.”
AstraZeneca has started mass production of the vaccine across 10 countries.
The company says it will have the equivalent of 20 million ‘full-strength’ doses in bulk form ready to be put into vials in the UK by the end of the year, and another 4 million ‘fill and finished’ in vials ready for distribution.
By the end of Q1 2021 there will be the equivalent of 40 million doses in bulk form in the UK.
Professor Pollard added: “These findings show that we have an effective vaccine that will save many lives.
“Excitingly, we’ve found that one of our dosing regimens may be around 90% effective and if this dosing regime is used, more people could be vaccinated with planned vaccine supply.
“Today’s announcement is only possible thanks to the many volunteers in our trial, and the hard working and talented team of researchers based around the world.”
The Oxford-AstraZeneca jab can be stored at normal fridge temperature – which would make storage and distribution much easier – compared to the Pfizer vaccine which needs to be kept at -70C.