The University of Oxford hopes to present late-stage trial results on its Covid-19 vaccine candidate this year though its top scientific investigator cautioned it would still take some time for life to return to normal.

A vaccine that works is seen as a game-changer in the battle against the coronavirus, which has killed more than 1.2 million people worldwide, shuttered swathes of the global economy and turned normal life upside down for billions of people.

"I'm optimistic that we could reach that point before the end of this year," Oxford Vaccine Trial Chief Investigator Andrew Pollard told British MPs of presenting trial results this year.

Prof Pollard said working out whether or not the vaccine worked would likely come this year, after which the data would have to be carefully reviewed by regulators and then a political decision made on who should get the vaccine.

"Our bit - we are getting closer to but we are not there yet," said Prof Pollard, the director of the Oxford Vaccine Group.

Asked if he expected the vaccine would start to be deployed before Christmas, he said: "There is a small chance of that being possible but I just don't know."

The Oxford/AstraZeneca vaccine is expected to be one of the first from big pharma to be submitted for regulatory approval, along with Pfizer and BioNTech's candidate.

Work began on the Oxford vaccine in January.

Called AZD1222, or ChAdOx1 nCoV-19, the viral vector vaccine is made from a weakened version of a common cold virus that causes infections in chimpanzees.

Prof Pollard said the US Food and Drug Administration had set the bar for a vaccine being at least 50% effective - a level that would have a transformative impact on the pandemic.

"But to be able scientifically able to test 50% is a lot harder - you need a lot more cases to occur in the trials," he said.

"So I think we are all hoping the vaccine will be more effective than that which means we will have an answer sooner."

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If Oxford's vaccine works, it would eventually allow the world to return to some measure of normality after the tumult of the pandemic.

Asked what success looked like, he said: "I think good is having vaccines that have significant efficacy - so whether, I mean, that is 50%, 60%, 70%, 80%, whatever the figure is - is an enormous achievement.

"It means from a health system point of view, there are fewer people with Covid going into hospital, that people who develop cancer can have their operations of chemotherapy.

"It's a complete game changer and a success if we meet those efficacy end points."

But Prof Pollard, one of the world's top experts on immunology, said the world might not return to normal immediately.

"But unfortunately it doesn't mean we can all go back to normal immediately because it takes time to roll out vaccines, not everyone will take them," he said.

"We will still have people getting this virus because it is just too good at transmitting."