It came as a plan to develop vaccines within 100 days of a completely new pandemic was on Thursday questioned by the lead scientist on the Oxford jab.

Prof Dame Sarah Gilbert, who led the development of the AstraZeneca vaccine, said it was “going to take a lot longer than 100 days” to determine whether a jab would work against a new infection.

Last year, Sir Patrick Vallance, the government’s Chief Scientific Adviser, launched the “100 Days Mission” in partnership with G7 countries, which aims to have vaccines, testing and drugs available quickly in the event of an outbreak.

At a Royal Society event in London, Dame Sarah said it would be “wonderful” to have early access to treatments and jabs, but questioned whether the goal was achievable.

“What about the clinical development?” she asked. “What about knowing that the vaccine works? How are we going to achieve that, particularly when it’s a novel pathogen and not one that we already know about? That’s going to take a lot longer than 100 days.”

Sir Patrick said it was important to “start on the road”, adding: “It’s not going to be possible for lots of things for many, many, many, many years, but it provides a sort of an aiming point.”