(REUTERS) — Britain approved Pfizer’s COVID-19 vaccine on Wednesday, jumping ahead of the rest of the world in the race to begin the most crucial mass inoculation program in history with a shot tested in wide-scale clinical trials.

Prime Minister Boris Johnson touted the green light from the U.K.’s medicine authority as a global win and a ray of hope amid a 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 which has killed nearly 1.5 million people, hammered the world economy and upended normal life for billions.

Britain’s Medicines and Healthcare products Regulatory Agency (MHRA) granted emergency use approval to the Pfizer-BioNTech vaccine, which it says is 95 percent effective in preventing illness, just 23 days since Pfizer published the first data from its final stage clinical trial.

“Fantastic news,” Johnson told parliament, though he cautioned that people should not get too 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.”

The world’s big powers have been racing for a vaccine for months to begin the long road to recovery, and getting there first may be seen as a coup for Johnson’s government, which has faced criticism over its handling of the crisis.

The approval of a shot for use close to a year since the novel coronavirus emerged in Wuhan, China, is a triumph for science, Pfizer boss Albert Bourla and his German biotechnology partner BioNTech.

Both the U.S. and the European Union’s regulator are sifting through the same Pfizer vaccine trial data, but have not yet given their approval.

Britain’s breakneck speed drew criticism from Brussels where, in an unusually blunt statement, the EU’s drugs regulator said its longer procedure was more appropriate as it was based on more evidence and required more checks.

British leaders said that, while they would love to get a shot themselves, priority had to be given to those most in need — the elderly, those in care homes and health workers.

Amid the celebratory rhetoric, Germany’s ambassador to Britain Andreas Michaelis publicly scolded a British minister for presenting it as a national triumph.

“I really don’t think this is a national story,” Michaelis said. “In spite of the German company BioNTech having made a crucial contribution, this is European and transatlantic.”

“No corners cut”

The U.S. drugmaker said Britain’s emergency use authorization marked a historic moment in the fight against COVID-19. Pfizer announced its vaccine breakthrough on Nov. 9 with stage III clinical trial results.

“This authorization is a goal we have been working toward since we first declared that science will win, and we applaud the MHRA for their ability to conduct a careful assessment and take timely action to help protect the people of the U.K.,” said CEO Bourla.

Britain’s medicines regulator 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.”

“With 450 people dying of COVID-19 infection every day in the U.K., 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.

The U.S. Food and Drug Administration (FDA) will make a decision on emergency use authorization on the Pfizer/BioNTech vaccine in days or weeks after a panel of outside advisors meets on Dec. 10 to discuss whether to recommend it. The FDA often but not always follows the panel’s advice.

The European Medicines Agency (EMA) said it could give emergency approval for the shot by Dec. 29.

“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.

BioNTech said it expected the FDA and EMA to make a decision in mid-December.

Anti-poverty campaigners, meanwhile, warned against rich countries hoarding vaccines at the expense of poorer ones. “The worst thing we can do at this moment is allow a small number of countries to monopolies access to vaccines like this,” said Romilly Greenhill, U.K. director of the ONE organization.

I strongly urge people to take up the vaccine, but it is no part of our culture or our ambition in this country to make vaccines mandatory — U.K. PM Boris Johnson

First in line?

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.

“I strongly urge people to take up the vaccine, but it is no part of our culture or our ambition in this country to make vaccines mandatory,” Johnson said.

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 the vaccine must be stored.

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.

Health Secretary Matt Hancock said hospitals were ready to receive the shots and vaccination centers would be set up across the country, but he admitted distribution would be a challenge given storage at temperature typical of an Antarctic winter.

Pfizer has said the shots can be kept in thermal shipping boxes for up to 30 days. Afterwards, the vaccine can be kept at fridge temperatures for up to five days.

Other frontrunners in the vaccine race include U.S. biotech firm Moderna, which has said its shot was 94 percent successful in late-stage clinical trials, and AstraZeneca, which said last month its COVID-19 shot was 70 percent effective in pivotal trials and could be up to 90 percent effective.