Prime Minister Boris Johnson will hold a Downing Street press conference today at 5pm.

The PM will be joined by deputy chief medical officer Professor Jonathan Van-Tam and Brigadier Joe Fossey. 

It comes as pharmaceutical company Pfizer has announced its coronavirus vaccine candidate is more than 90 per cent effective in preventing Covid-19 during a major 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.

“We will know whether the vaccine is both safe and effective once the safety data has been published and only then can licensing authorities consider making it available to the public.

“In the meantime, the NHS stands ready to begin a vaccination programme for those most at risk once a Covid-19 vaccine is available before being rolled out more widely.

“In total, we’ve procured 40 million doses of the Pfizer candidate vaccine, with 10 million of those doses being manufactured and available to the UK by the end of the year if the vaccine is approved by the regulators.”

Pfizer, which is developing the mRNA-based vaccine with BioNTech, said the results were from a independent interim analysis of the results of its phase three clinical study.

Dr Albert Bourla, Pfizer chairman and CEO, said: “Today is a great day for science and humanity. The first set of results from our phase three Covid-19 vaccine trial provides the initial evidence of our vaccine’s ability to prevent Covid-19.

“We are reaching this critical milestone in our vaccine development programme at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen.

“With today’s news, we are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis. We look forward to sharing additional efficacy and safety data generated from thousands of participants in the coming weeks.

“I want to thank the thousands of people who volunteered to participate in the clinical trial, our academic collaborators and investigators at the study sites, and our colleagues and collaborators around the world who are dedicating their time to this crucial endeavour.

“We could not have come this far without the tremendous commitment of everyone involved.”