Pfizer claims its coronavirus vaccine is 95% effective and has passed safety checks, in a huge breakthrough in the battle against the disease.
The drug, developed in collaboration with German partner BioNTech SE, is due to be distributed across the UK before the end of this year.
Health Secretary Matt Hancock this week told the House of Commons he had “tasked the NHS with being ready from any date from December 1” to roll out the vaccine.
The firm says now it can now apply for emergency use in the US after publishing interim results from a massive trial including 43,500 people across six countries.
Pfizer said the drug's effect was consistent across age and ethnicity demographics, and that there were no major side effects – sparking hopes immunisation could be rolled out across the world.
Perhaps most promisingly, the jab appears to be more than 94% effective in protecting adults over the age of 65 – the group most at risk from coronavirus.
That data was based on the first 94 volunteers to develop Covid-19, but further figures released on Wednesday, November 18, are based on the first 170 cases of the virus in the clinical trial.
Of these 170 Covid-19 cases, 162 were observed in the placebo group versus eight in the vaccine group.
There were 10 severe cases of Covid-19 overall, with nine in the placebo group and one in the vaccine group.
The UK has secured 40 million doses in total of the vaccine, with 10 million due in the country by the end of the year if the jab is approved.
People will need two doses, meaning not enough vaccines have been secured for the entire UK population.
Another jab, from US firm Moderna, was shown this week in early data to be almost 95% effective.
The UK has ordered five million doses of that jab, and also awaits the results of the Oxford University and AstraZeneca vaccine study - which is due to report soon.
Changes to the Human Medicine Regulations announced in October will allow the Medicines and Healthcare products Regulatory Agency (MHRA) to authorise temporary supply of vaccines if one becomes available before 2021.
Pfizer and BioNTech expect to be able to produce up to 50 million vaccine doses globally in 2020 and up to 1.3 billion in 2021.
The company's Chief Executive Officer Albert Bourla said: "The study results mark an important step in this historic eight-month journey to bring forward a vaccine capable of helping to end this devastating pandemic.
"We continue to move at the speed of science to compile all the data collected thus far and share with regulators around the world.
"With hundreds of thousands of people around the globe infected every day, we urgently need to get a safe and effective vaccine to the world."
On Monday, November 16, Moderna said its Covid vaccine could prevent 94.5% of people from getting the disease.
Thirty-thousand people were given the vaccine in the US in a trial, and preliminary analysis was based on the first 95 to develop Covid-19 symptoms.
Just five had symptoms after taking the vaccine, and the other 90 had been given the placebo.
There were 11 cases of severe coronavirus in the trial, but none occurred in those who were immunised.