The finding was the result of the first independent analysis of any Covid-19 vaccine in phase 3 trials — the final stage before commercial licensing. The study found that 94 participants who received the two-dose vaccine were protected against the disease 28 days after their first inoculation.

“To me, this is the best possible outcome,” Ugur Sahin, co-founder and chief executive of BioNTech told the Financial Times, while Pfizer boss Albert Bourla said it was “a great day for science and humanity”.

The risk-benefit profile is in clear favour of benefit, it fulfils all the criteria to be processed fast,” Mr Sahin added. He said that the drug would be submitted to authorities for emergency approval within a matter of weeks.

The results far exceed the US Food and Drug Administration’s criteria for approving a Covid-19 vaccine, which mandates an efficacy of at least 50 per cent in placebo-controlled trials. No vaccine is 100 per cent effective, according to the World Health Organization.

Pfizer and BioNTech said that up to 50 million doses of the vaccine — which would be the first vaccine to use novel mRNA technology — could be manufactured this year, and a further 1.3 billion doses produced in 2021.

Vaccine

Pfizer previously said that it expects to roll out its vaccine in Ireland in 2021. Its site at Grange Castle in Dublin is working on quality testing batches of the vaccine candidate that are being manufactured at the group’s plant in Belgium.

The Pfizer and BioNTech vaccine uses messenger RNA (mRNA) technology, which relies on synthetic genes that can be generated and manufactured in weeks, and produced at scale more rapidly than conventional vaccines.

Mr Sahin said BioNTech and Pfizer would “use a fair approach” when it came to distributing the first doses of the vaccine, adding that they would prioritise deliveries to countries where it had been approved for use.

Pfizer expects to seek broad US emergency use authorization of the vaccine for people aged 16 to 85. To do so, it will need to have collected two months of safety data on around half of the study’s roughly 44,000 participants, expected in late November.

“I’m near ecstatic,” Bill Gruber, one of Pfizer’s top vaccine scientists, said in an interview. “This is a great day for public health and for the potential to get us all out of the circumstances we’re now in.”

Pfizer said the interim analysis was conducted after 94 participants in the trial developed COVID-19, examining how many of them received the vaccine versus a placebo.

The company did not break down exactly how many of those who fell ill received the vaccine. Still, over 90 per cent effectiveness implies that no more than eight of the 94 people who caught COVID-19 had been given the vaccine, which was administered in two shots about three weeks apart.

To confirm its 50 per cent efficacy rate, Pfizer said it will continue the trial until there are 164 COVID-19 cases among participants. Given the recent spike in US infection rates, that number could be reached by early December, Gruber said.

The data have yet to be peer-reviewed or published in a medical journal. Pfizer said it would do so once it has results from the entire trial.

Downing Street welcomed the results from Pfizer’s vaccine tests as “promising” and said the UK will have procured 10 million doses by the end of the year to be given out if it is approved.

The Prime Minister’s official spokesman said: “The results are promising and while we are optimistic of a breakthrough, we must remember there are no guarantees.”