Scientific and medical experts have hailed Pfizer’s vaccine news as a huge relief and "major step" in the fight against Covid-19.

Professor Peter Horby, one of the academics who discovered that dexamethasone could increase the survival rate among Covid patients, said he smiled from “ear to ear” after seeing the findings.

And he’s not the only one to praise the “exceptionally good news”, after Pfizer and BioNtech said that their vaccine was found to be 90 per cent effective - with no safety concerns.

Speaking to BBC Radio 4’s World at One, Professor Sir John Bell of Oxford University said he was “optimistic” and that we could expect more than one vaccine to be rolled out in the UK before the end of the year, or early in the new year.

And when asked whether we could be confident that life would return back to normal by spring, Professor John Bell replied “yes, yes, yes”, and that he could say it with “some confidence.”

Professor Fiona Watt, executive chair of the Medical Research Council, said: “This is very encouraging news – and provides grounds for optimism that other vaccines will also show benefits.

“What really strikes me though is the fantastic contribution of the many volunteers who have taken part in the trial, including over 40% from diverse backgrounds. Without their altruism, the trial could not have gone ahead.”

Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh, said: “At face value, this is exceptionally good news: a vaccine that is 90% effective at preventing symptomatic cases of Covid-19 and with millions of doses available by the end of the year.

“However, the full data set on which the claim is based has not yet been released and so we don’t know exactly what has been found.

“The two companies are at pains to point out that the trial participants are ethnically diverse, which is good, but say nothing about the age of people in the trial. If a vaccine is to reduce severe disease and death, and thus enable the population at large to return to their normal day-to-day lives, it will need to be effective in older and elderly members of our society.

“We also know nothing yet about the severity of cases that were seen in the trial, whether infection or infectiousness was prevented, or how long the immunity is expected to last.

“But I think we have reason to be cautiously optimistic.”

Professor Gordon Dougan, infectious disease and vaccine specialist from the University of Cambridge, said: “It is tremendous news if it turns out to be true, which I think it will do.

“A 90% efficacy hit in the short-term interim analysis is good news. I’m not entirely surprised but I’m delighted with the news.

“I think we will get more news on other vaccines in a relatively short period of time.”

Ian Jones, professor of virology at the University of Reading, said the Pfizer trial data shows “really impressive protection and no reported adverse events”.

He said: “Of all the current vaccines currently in development the BioNtech product always looked like the most bang-per-buck as it is entirely focused on the part of the virus that binds to the human cell: the receptor-binding domain.

“The questions around its use were about the ability to manufacture at scale and the possible toxicity associated with a directly injected RNA product.

“The trial data show excellent results in both of those areas, really impressive protection and no reported adverse events.”

Dr Michael Head, senior research fellow in global health at the University of Southampton, added: “This cautiously sounds like an excellent result from the phase three trials. But we should remain a little cautious.

“If the final results show an effectiveness of anywhere near 90% with response in elderly and ethnic minority populations, that is an excellent result for a first generation vaccine.”

Dr Head added that if the vaccine is approved for use by regulators then there could be difficulties posed by logistics and distribution due to the temperature that the vaccine needs to be stored at.

He said: “It has been reported that the vaccine requires storage at minus 70C (minus 94F) and that is not necessarily routinely available in most health centres even in the UK, let alone globally.”

This is very encouraging news – and provides grounds for optimism that other vaccines will also show benefits

Professor Azra Ghani, chair in infectious disease epidemiology at Imperial College London, said that long-term efficacy data would come over the next weeks and months.

Prof Ghani said: “These new results represent the first demonstration of substantial efficacy of a vaccine candidate against Covid-19 disease, which is very welcome news.

“The efficacy estimate is based on seven days of follow up of participants following the second dose. Further data in the coming weeks and months will provide a better picture of longer-term vaccine efficacy.”

Daniel Davis, professor of immunology at the University of Manchester, said: “This is a watershed moment. For the first time, there is evidence that one of the possible vaccines for Covid-19 can protect people from the disease.

“It is early days still and it is important to remember that there are caveats: we need to be able to scrutinise the data independently, and we don’t yet know how long immunity may last for.

“The safety data isn’t yet sufficiently robust so that this medicine could be approved formally yet.

“And this type of vaccine also poses particular problems for being distributed around the world because it has to be stored at very cold temperatures.

“But despite these issues, this is an enormously thrilling moment. As a scientist, I am nervous of over-hyping a medical breakthrough, but this is genuinely a big moment for humankind.

“This also bodes very well for other candidate vaccines which are undergoing similar tests in people now. At last, it feels like we are turning a corner.”

Prof Horby, professor of emerging infectious diseases and global health in the Nuffield Department of Medicine at the University of Oxford, said: “This news made me smile from ear to ear.

“It is a relief to see such positive results on this vaccine and bodes well for Covid-19 vaccines in general.

“Of course we need to see more detail and await the final results, and there is a long, long way to go before vaccines will start to make a real difference. But this feels to me like a watershed moment.”