By Joseph Walker and Jenny Strasburg 

LONDON -- The U.K. authorized a Covid-19 vaccine developed by the University of Oxford and AstraZeneca PLC, opening the door for the rollout of millions of doses in a country where infections have surged amid a more infectious variant of the virus.

The green light represents the third emergency-use approval of a Western-developed vaccine this month and comes as cases rise sharply in the U.S. and Europe. A shot by Pfizer Inc. and Germany's BioNTech SE and one by Moderna Inc. have both been cleared in the U.S. and are being distributed there.

AstraZeneca's shot -- less effective in clinical trials than its rivals' injections -- won't be available in the U.S. until the Food and Drug Administration reviews large-scale trials still being conducted there and decides to authorize its use.

The U.K. authorization comes as the country battles a new, potentially more contagious variant of the coronavirus. The mutated virus triggered travel bans recently on visitors and goods from Britain, ratcheting up the political urgency for a speedy vaccine rollout here. Pfizer's shot is already available in the U.K., where Prime Minister Boris Johnson said on Dec. 21 that a half million of the first of a two-dose regimen have been administered.

Scientists have said that the three Covid-19 vaccines authorized so far should be similarly effective against the new British variant as they have been in clinical trials, a view AstraZeneca executives share, according to a person familiar with the matter. The new variant could be as much as 70% more transmissible than more established forms of Covid-19, government officials say.

Pfizer has promised the U.K. millions more doses by the end of the year, but the AstraZeneca and Oxford shot -- made at facilities in the country and elsewhere -- promises to quicken the rate of inoculations by the country's state-run health-care system. The National Health Service will determine which shot to provide people depending on supply.

In clinical trials, the AstraZeneca vaccine proved to be significantly less effective in preventing symptomatic Covid-19 than the vaccines by Pfizer and Moderna. But it still exceeded a key hurdle of 50% efficacy set earlier this year by regulators including the FDA, established as a benchmark for emergency authorization to prevent hospitalizations and deaths.

AstraZeneca said Wednesday it will supply millions of doses in the first quarter of next year, without specifying an exact number. The U.K. has ordered up to 100 million doses of the vaccine, enough for 50 million people.

The company said the vaccine will be used for adults 18 years and older. It didn't provide any further guidance on the age of recipients or dosing size.

The vaccine provided between 62% and 90% effectiveness against symptomatic Covid-19, depending on dosage size. Two full doses about a month apart led to the 62% reading, while a small subset of trial volunteers who received a lower initial dose followed by a second standard dose showed a 90% efficacy reading. That subset of trial participants were all 55 years or younger. Oxford and AstraZeneca scientists have said they are unsure why that regimen would be more effective.

The partners previously said they were deferring to regulators to analyze the combined clinical-trial results and recommend dosage levels based on the data. The U.K.'s Medicines and Healthcare products Regulatory Agency is expected soon to provide detailed recommendations about the vaccine's use.

Write to Joseph Walker at joseph.walker@wsj.com and Jenny Strasburg at jenny.strasburg@wsj.com

 

(END) Dow Jones Newswires

December 30, 2020 02:53 ET (07:53 GMT)

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