LONDON: 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 programme in history with a shot tested in wide-scale clinical trials.

Prime Minister Boris Johnson touted the green light from Britain's medicine authority as a global win and a ray of hope amid the pandemic, though he recognised 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."

The world's big powers have been racing for a vaccine for months and coming first may be seen as a coup for a government that has faced criticism over its handling of the crisis.

Both the US and EU regulators are sifting through the same Pfizer vaccine trial data, but have yet to give their approval. 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. 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.