The UK government bought the rights to 40m doses of the vaccine in July as it developed a portfolio of hopeful candidates against covid.
Pfizer, which will manufacture the drug in the US, Germany and Belgium, says it and German partner BioNtech will produce up to 50m doses this year and 1.3bn next year.
Up to 10m doses could be made available to the UK by the end of the year if it passes final safety checks, the UK Government said this afternoon.
However, there are UK protocols that ensure the most vulnerable, such as care home residents and staff, get vaccinated first – with frontline health workers next in line.
Working age adults in good health will be the last to receive a vaccine under interim UK guidelines – which could mean next summer at the earliest.
There are also concerns that anti-vaxxer sentiment could hinder widespread take-up – with up to 80 per cent coverage likely to be necessary to bring the pandemic to heel.
Last month the Royal Society’s DEVLE group warned of a number of potential challenges with the first phase of new vaccines.
These concerns included the fear that they may not work equally well in all age groups, may provide short-lived immunity and may be difficult to manufacture and distribute at scale.
Experts noticed that today’s Pfizer announcement did not indicate how effective its vaccine was in older people, who are at far greater risk of serious illness and death from covid.
Nor did it address reports that the vaccine must be stored at -70C to -80C prior to being administered.
Pfizer’s trials have involved about 44,000 volunteers in Argentina, Brazil, Germany, South Africa, Turkey and the United States, but the trials are not yet complete.
Two doses per person are required – and its results reported today, while apparently preventing covid in “more than 90 per cent” of trial volunteers, only showed it was of benefit seven days after the second dose was received.
This means that social distancing will be required in the UK for many months, as it will take time until a sufficient proportion of the population is inoculated for it to have an impact on the spread of the virus.
This also assumes that the vaccine is able to prevent onward transmission of the virus in addition to protecting individuals against falling ill.
Dr Stephen Griffin, of Leeds university, warned that today’s announcement must not “seed complacency”.
He said: “It will likely be several months following a potential emergency regulatory approval until the manufacture and roll out of the vaccine have reached enough of our population to have an impact.
“We must remember that tens of thousands of people are being infected with this virus every day within the UK, putting immense strain on our healthcare systems and causing hundreds of deaths on a daily basis.”
Professor Peter Horby, who is leading the rival Oxford vaccine trials, said today that the Pfizer announcement “made me smile from ear to ear” and said it felt like a “watershed moment”.
Stage-3 results from the Oxford trial are expected “in the coming months” if transmission rates of the virus remain high, his colleague Professor Andrew Pollard said.
Professor Pollard added that several potential vaccines needed to work “for the best possible results for humanity”.
He said the significance of the Pfizer announcement was that it showed it was possible to create a vaccine, which until today had not been certain.
The Pfizer vaccine is a mRNA vaccine – the same type as Imperial College London researchers are trialling – but different to the Oxford adenovirus vaccine, which uses a weakened version of the virus that causes the common cold in chimpanzees.
Today the Department for Business, Energy and Industrial Strategy said the Pfizer results were “very promising” but said the vaccine would not be rolled out until safety data had been checked.
A Government spokesperson said: “The results from Pfizer/BioNtech are very promising and we have procured 40 million doses of their vaccine.
“While we are optimistic of a breakthrough, we must remember that there are no guarantees.
“We will know whether the vaccine meets robust standards of safety and effectiveness once their safety data has been published, and only then can the medicines regulator can consider whether it can be made it available to the public.
“Once approved, the NHS stands ready to begin a vaccination programme for those most at risk, as currently recommended by the independent JCVI [Joint Committee on Vaccination and Immunisation], before being rolled out more widely.”
The UK has secured early access to more than 350 million vaccine doses. The others in the Government’s portfolio are being made by Novavax (currently in phase 2 clinical trials), Janssen ( phase 2), GSK/Sanofi Pasteur (phase 1) and Valneva (pre-clinical trials).
Dr Jeremy Farrar, director of Wellcome, said the vaccine “could be more effective than we ever hoped for” but said there were challenges ahead.
He said: “If large parts of the world remain shut down because rich countries hoard supplies, we will all continue to suffer.
“Any Covid-19 vaccine will face the largest and fastest vaccine manufacturing scale-up and roll-out in history. We must not underestimate the phenomenal logistical challenge that lies ahead.”
Dr Alexander Edwards, of University of Reading, said: “The next stage … will still be a monumental undertaking.”
Professor Gary McLean, of London Metropolitan University, said: “The vaccine is still some way off yet and will not immediately replace the established control measures currently in place… This will take time and effort so will likely be well into 2021 before we see general availability.”