AZN AstraZeneca PLC

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 distributing millions of doses in a country where a more infectious variant of the coronavirus has contributed to surging cases.

British health officials also recommended a delay of up to three months between both doses of the vaccine, guidance that also applies to the shot developed by Pfizer Inc. and BioNTech SE that the U.K. authorized earlier this month. The delay will allow inoculations to reach more people more quickly as the variant pushes new cases to records and hospitalizations soar.

The green light represents the third emergency-use approval of a Western-developed vaccine this month and comes as cases rise sharply in Europe and the U.S., which reported its first confirmed case of the variant Tuesday. The Pfizer-BioNTech shot and one developed by Moderna Inc. have been cleared in the U.S.

The Oxford-AstraZeneca vaccine stands out on price, convenience and global ambition. AstraZeneca has promised to make as many as three billion doses available in 2021 -- more than any other Covid-19 vaccine maker -- and at a cheaper price. The U.K. company says it won't profit from the shot during the pandemic, or ever in the case of poorer countries. The vaccine also can be transported and stored for months with normal refrigeration, making it easier to distribute where people and health-care networks are sparse or underfunded. The two other Western vaccines in use require ultracold temperatures for all but a few days or weeks.

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 whether to authorize its use.

The mutated virus recently led some nations to ban visitors and goods from Britain, increasing the political urgency for a speedy vaccine rollout here. The government has said that more than 600,000 doses of the Pfizer-BioNTech vaccine have been administered.

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

The U.K. medicines regulator said the vaccine can be administered to people 18 years and older. The authorization clears the use of two standard vaccine doses, a regimen that was 62% effective in preventing symptomatic Covid-19 in an interim analysis of trials involving about 11,600 people in the U.K. and Brazil.

In the same study, a small subset of volunteers of ages 55 and younger were given a half-dose shot followed by a standard dose. That subset showed a higher protection rate of 90%. The U.K. government hasn't authorized the use of the half-dose regimen.

"We felt the results were not borne out by the full analysis," Munir Pirmohamed, a pharmacologist who chairs the government's advisory group that advised on the regulator's recommendations, said Wednesday.

U.K. officials said they authorized the vaccine Tuesday and released the first batches that night.

They advised that no preference generally should be given between the two vaccines so far authorized by the U.K. The higher efficacy shown by the Pfizer vaccine isn't directly comparable with that of the Oxford-AstraZeneca shot, officials said, because of scientific and clinical-trial differences.

AstraZeneca and U.K. health officials said the two-dose regimen is flexible in terms of when the second dose should be given, anywhere from four weeks to 12 weeks after the first.

Delaying the second dose would help stretch supplies so more Britons get a first shot sooner. But the vaccine's full protection -- benefits shown in clinical trials to prevent hospitalization -- kicks in only after the second dose.

U.K. health officials said Wednesday the updated second-dose guidance also applies to the Pfizer-BioNTech shot already being administered in the country. Previously, the second dose was recommended 21 days after the first. U.K. officials changed that Wednesday to "within 12 weeks," citing the latest scientific advice. The vaccine's makers have said full protection doesn't start until at least seven days after the second dose.

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 accelerate inoculations by the country's state-run health-care system. The National Health Service will determine which shot to provide people depending on supply.

AstraZeneca said Wednesday it would 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, enough for 50 million people.

Government advisers behind the authorization said the 90% efficacy shown in the half-dose regimen might have been caused by the longer period between the first and second doses in that trial subgroup, rather than by the half-dose itself. They said the analysis of the half-dose subgroup contributed to authorities' decision to recommend up to 12 weeks between doses.

The advisers said for the full-dose regimen, immunity kicks in roughly three weeks after the first dose. They estimated 70% effectiveness in the vaccine during the period from three weeks after the first dose through the next three months. They said it isn't clear whether that number will hold up in fuller clinical trials.

It is unclear how quickly other nations might authorize the vaccine. A large clinical trial is under way in the U.S., where AstraZeneca executives expect to have full trial data to submit by February, according to a person familiar with the matter. They have been submitting batches of data to European regulators and are poised for potential authorization across the European Union by February, the person said.

AstraZeneca's U.S. study has so far enrolled 29,700 volunteers out of a planned 30,000 volunteers, and an emergency-use authorization could be granted in early April if the study results are positive, Moncef Slaoui, chief adviser to the federal Operation Warp Speed initiative, told reporters Wednesday. If the vaccine is authorized that month, the U.S. government expects several tens of millions of doses to be available for distribution, he said.

Dr. Slaoui said he has no doubt that the vaccine is effective in preventing severe disease in the population where it has been tested. However, he said, "For me, the biggest question mark, frankly, is efficacy in the elderly population that needs to be further documented" because the U.K. and Brazilian studies didn't enroll enough older volunteers early in the trials.

Oxford and AstraZeneca emerged early this year as front-runners in the race to develop a Covid-19 vaccine before falling behind competitors that completed clinical trials faster. Developed by scientists at Oxford's Jenner Institute, the vaccine uses a weakened cold virus to courier genetic material from the coronavirus into cells and trigger immunity.

AstraZeneca agreed in April to co-develop Oxford's technology and distribute it around the world at no profit during the pandemic. By November, the company had agreements to supply three billion doses to every region in the world.

The partners have faced setbacks along the way to Wednesday's milestone. In May, they launched a combined Phase 2 and 3 clinical trial in the U.K. aimed at enrolling more than 10,000 volunteers and obtaining initial results by August. But the study progressed slower than initially hoped, partly because of relatively low infection rates in the U.K. for much of the summer and fall.

By the time AstraZeneca launched a planned Phase 3 U.S. study of 30,000 volunteers in late August, the company was trailing Pfizer and Moderna, which had begun similarly sized studies a month earlier. Within two weeks, AstraZeneca paused all its studies globally after a U.K. volunteer had an unexplained illness. U.K. regulators allowed studies to resume quickly, but the U.S. trial remained grounded for more than six weeks before U.S. regulators lifted the hold in October.

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

(END) Dow Jones Newswires

December 30, 2020 16:12 ET (21:12 GMT)

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