One option being explored to speed up the availability of a vaccine would involve the US Food and Drug Administration awarding “emergency use authorisation” (EUA) in October to a vaccine being developed in a partnership between AstraZeneca and Oxford university, based on the results from a relatively small UK study if it is successful, the people said.

The AstraZeneca study has enrolled 10,000 volunteers, whereas the US government’s scientific agencies have said that a vaccine would need to be studied in 30,000 people to pass the threshold for authorisation. AstraZeneca is also conducting a larger study with 30,000 volunteers, although the results from that will come after the smaller trial.

Making a vaccine available before the election could allow US president Donald Trump to claim he has turned the tide on a virus that has killed more than 170,000 Americans following widespread criticism of his handling of the pandemic. In his convention speech on Thursday night, Joe Biden, Mr Trump’s Democratic opponent, said that the US response to the virus was the “worst performance of any nation”.