LONDON (UPDATE) — A 90-year-old British grandmother became the first person in the world to receive Pfizer-BioNTech's COVID-19 vaccine outside clinical trials, just days after the United Kingdom approved use of the drug.

• UK approves Pfizer-BioNTech COVID-19 vaccine, first in the world

Margaret Keenan received a dose of the vaccine on Tuesday at University Hospital Coventry and Warwickshire.

Video via Reuters

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She was the first among the batch of Britons inoculated Tuesday as Britain began the mass vaccination of its population against COVID-19, becoming the first Western nation to do so in a global endeavor that poses one of the biggest logistical challenges in peacetime history.

On a day dubbed "V-Day," health workers started inoculating people with a shot developed by Pfizer and BioNTech, with the country a test case for the world as it contends with distributing a compound that must be stored at -70C.

Britain is the first country globally to begin mass inoculations with that vaccine, one of three shots that have reported successful results from large trials after being developed in record time.

"If we manage to do that for everybody who is vulnerable to this disease, then we can move on and we can return to normal," said Health Minister Matt Hancock, who described the start of vaccinations as "V-Day."

The launch will fuel hope that the world may be turning a corner in the fight against a pandemic that has killed more than 1.5 million people and crushed economies.

Britain, the worst-hit European country with over 61,000 deaths, has ordered enough supplies of the Pfizer-BioNTech shot to vaccinate 20 million people. The developers said it was 95% effective in preventing illness in final-stage trials.

Russia and China have both already started giving domestically produced vaccine candidates to their populations, though before final safety and efficacy trials have been completed.

'DECISIVE TURNING POINT'

In Britain, about 800,000 doses are expected to be available within the first week, with care home residents and carers, the over-80s and some health service workers prioritized.

The country is relatively small with good infrastructure. Yet the logistical challenges in distributing the vaccine, which only lasts five days in a regular fridge, mean it will first go to dozens of hospitals and cannot yet be taken into care homes.

Bigger tests could await for the Pfizer-BioNTech shot, as well as a vaccine from Moderna, which was found to have a similar level of success in trials and is based on the same mRNA genetic technology that requires such ultra-cold storage.

Transport and distribution could prove more challenging in bigger countries, including the United States and India which have been worst-hit by the pandemic, and in hotter nations.

The third vaccine to have had trial success, developed by AstraZeneca and Oxford University, is viewed as offering one of the best hopes for many developing countries because it is cheaper and can be transported at normal fridge temperatures. Late-stage trials found it had an average success rate of 70%.

Britain approved the Pfizer/BioNTech vaccine for emergency use less than a week ago, and is rolling it out ahead of the United States and European Union, from which it will finally part ways at the end of the year.

"The deployment of this vaccine marks a decisive turning point in the battle with the pandemic," said Simon Stevens, head of the publicly funded NHS health service.

In total, Britain has ordered 40 million doses of the Pfizer-BioNTech shot. As each person requires two doses, that is enough to vaccinate 20 million people in the country of 67 million.

But the country is spreading it bets and has ordered 357 million doses of seven different COVID-19 vaccines in all.