Prime Minister Boris Johnson touted the green light from Britain's medicine authority as a global win and a ray of hope for the end of the pandemic, though he recognized the logistical challenges of vaccinating an entire country of 67 million.
Britain's move raised hopes that the tide could soon turn against a virus that has killed nearly 1.5 million people globally, hammered the world economy and upended normal life for billions since it emerged in Wuhan, China, a year ago.
Britain's Medicines and Healthcare products Regulatory Agency (MHRA) granted emergency use approval to the vaccine developed by Pfizer and German biotechnology partner BioNTech , which they say is 95% effective in preventing illness, just 23 days after Pfizer published the first data from its final stage clinical trial.
"Fantastic news," Johnson told parliament, though he cautioned that people should not get carried away.
"At this stage it is very, very important that people do not get their hopes up too soon about the speed with which we will be able to roll out this vaccine."
International drugmakers and researchers have been racing to develop vaccines for months and Britain's authorisation coming first may be seen as a coup for a government that has faced criticism over its handling of the crisis.
U.S. and EU regulators are sifting through the same Pfizer vaccine trial data, but have yet to give their approval.
Britain's swift decision drew criticism from Brussels where, in an unusually blunt statement, the EU regulator said its longer procedure was more appropriate and based on more evidence.
Johnson might be persuaded to take a COVID-19 shot on television to show it was safe, but he would not have one before those in greater need, his press secretary said.
Britain said it would start vaccinating those most at risk of dying early next week after it gets 800,000 doses from Pfizer's manufacturing center in Belgium, and UK Health Secretary Matt Hancock said tests on that first batch had been completed.
Hours after the British announcement, President Vladimir Putin ordered Russian authorities to begin mass voluntary vaccinations next week. Russia will have produced 2 million doses of its own vaccine within the next few days, Putin said.
Pfizer vaccine executive Ralf Rene Reinert said other countries were looking to emulate Britain.
"The UK is leading, and now let's see how the other countries move forward. And Pfizer will do everything to exchange all the data packages with every regulatory agency," he said.
German Health Minister Jens Spahn said EU member states could have issued similar emergency approvals, but Europe had decided to move forward as one.
"It's very important we do this to help promote trust and confidence in this authorisation," he said.
Britain is bound by European law until the transition period ends on Dec. 31, but opted for emergency approval anyway.
Asked if the speedy approval was a "big Brexit bonus," Johnson credited global efforts instead.
"It's a truly international thing and very, very moving to see it," the PM said.
'NO CORNERS CUT'
Pfizer shares rose almost 4% to their highest since July 2019 and BioNTech's U.S.-listed shares rose almost 5% after hitting record highs on Tuesday.
Global stocks were also higher over optimism the world can turn a corner in curbing the pandemic, although the gains were more muted than those seen in November, when Pfizer published the first trial results.
Britain's MHRA approved the vaccine in record time by doing a "rolling" concurrent analysis of data and the manufacturing process while Pfizer raced to conclude trials.
"No corners have been cut," MHRA chief June Raine said in a televised briefing from Downing Street, adding that the first data on the vaccine had been received in June and undergone a rigorous analysis to international standards. "Safety is our watchword."
The emergency use approval does not come with any associated volume cap or threshold, Pfizer UK's country manager said.
"With 450 people dying of COVID-19 infection every day in the UK, the benefits of rapid vaccine approval outweigh the potential risks," said Andrew Hill, senior visiting research fellow in the Department of Pharmacology at the University of Liverpool.
U.S. Health Secretary Alex Azar said the British move should inspire confidence.
"For the American people this should be very reassuring. An independent regulatory authority in another country has found this vaccine to be safe and effective for use," Azar told Fox Business Network.
The U.S. Food and Drug Administration will make a decision on emergency use authorization of the Pfizer/BioNTech vaccine in days or weeks after a panel of outside advisers meets on Dec. 10 to review the data and make its recommendation to the agency.
The European Medicines Agency (EMA) said it could give emergency approval for the shot by Dec. 29, while the World Health Organization said it was reviewing it for "possible listing for emergency use."
"The data submitted to regulatory agencies around the world are the result of a scientifically rigorous and highly ethical research and development program," said Ugur Sahin, chief executive and co-founder of BioNTech.
The company said it expected FDA and EMA to make decisions in mid-December.
Johnson said life would not return to normal right away, but there was now certainty that things would improve. He said the vaccines would not be mandatory but strongly encouraged eligible people to take them.
The speed of the rollout depends on how fast Pfizer can manufacture and deliver the vaccine - and the extreme temperature of -70C (-94F) at which it must be stored. It can be kept for five days in a regular fridge.
Britain has ordered 40 million doses of the Pfizer vaccine - enough for just under a third of the population as two shots are needed per person to gain immunity.