About 50,000 people worldwide are to be given shots of the Oxford University vaccine to test its safety and effectiveness, says Prof Andrew Pollard, part of the group developing it.
The potential vaccine, which is being developed by Oxford University and drug company AstraZeneca and is thought to be the most advanced candidate in clinical trials, is being tested on 10,000 people in the UK, and a further 10,000 in Brazil and South Africa. They also hope to enroll 30,000 people in US trials.
Prof Pollard told BBC Radio 4’s Today programme that the number of new cases in the coming weeks and months would determine how quickly the researchers could prove the vaccine offered effective protection.
But he said it is “just possible that if the cases accrue rapidly, we could have that data to put before regulators this year”.
Following reports that US President Donald Trump wants to speed up approval of the vaccine in time for the November election, AstraZeneca said it had not discussed any fast-tracking with regulators.