Interim data suggests 70% protection, but the researchers say the figure may be as high as 90% by tweaking the dose.

The results will be seen as a triumph, but come after Pfizer and Moderna vaccines showed 95% protection.

However, the Oxford jab is far cheaper, and is easier to store and get to every corner of the world than the other two.

So the vaccine will play a significant role in tackling the pandemic, if it is approved for use by regulators.

"The announcement today takes us another step closer to the time when we can use vaccines to bring an end to the devastation caused by [the virus]," said the vaccine's architect, Prof Sarah Gilbert.

The UK government has pre-ordered 100 million doses of the Oxford vaccine, and AstraZeneca says it will make three billion doses for the world next year.

Prime Minister Boris Johnson said it was "incredibly exciting news" and that while there were still safety checks to come, "these are fantastic results".