The UK Just Approved the Pfizer Covid Vaccine. What Happens Next?

LONDON — The first rigorously tested coronavirus vaccine was given a green light for use on Wednesday in Britain. Doses of the vaccine, made by the American pharmaceutical giant Pfizer and a small German company, BioNTech, will be injected starting next week, the government said.

In leaping ahead of the United States to allow mass inoculations, Britain added to the pressure on American drug regulators, who were summoned to the White House on Tuesday by President Trump’s chief of staff to explain why they were not ready to do the same.

Why did Britain authorize a vaccine before the U.S.?

The two countries vet vaccines differently.

Rather than accepting the findings of vaccine makers, American regulators painstakingly reanalyze raw data from the trials to validate the results, poring over what regulators have described as thousands of pages of documents. Dr. Stephen Hahn, the commissioner of the Food and Drug Administration, said on Tuesday that the F.D.A. “is one of the few regulatory agencies in the world that actually looks at the raw data.”

Regulators in Britain and elsewhere in Europe lean more heavily on companies’ own analyses. Instead of sifting through raw trial data and crunching the numbers themselves, regulatory agencies often will study a drugmaker’s reports and, unless there are anomalies, ground their decisions in company-provided documents.

The question of whether Britain had authorized a vaccine in haste, or the United States was wasting valuable time as the virus was killing about 1,500 Americans a day, provoked a spirited debate among scientists and industry experts on Wednesday. European regulators said that Britain’s authorization was so limited that it only applied to specific batches of the vaccine, a claim that Pfizer denied, and that British officials did not address.

Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the F.D.A.’s vaccine advisory panel, said in an interview on Wednesday that regulators’ success in approving vaccines, while minimizing unforeseen errors, justified a rigorous approach.

“That we’ve been able to get on top of viruses with such a minimal amount of casualties is remarkable,” he said, adding that American regulators were only days away from finishing their own review.

The F.D.A. has scheduled a meeting of an independent panel of experts for Dec. 10 to review Pfizer’s vaccine. British regulators seek opinions from a specialist committee, too, but that group has the flexibility to review data and meet as it needs to, allowing it to move more quickly.

“In the U.K., they’ve just been able to say, ‘We have the data, we’re having the meeting,’” said Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine.

To speed the process, Britain’s Medicines and Healthcare Products Regulatory Agency had its experts review vaccine data as it became available, and separate teams worked in parallel on different parts of the process, rather than one waiting for another to finish.

“If you’re climbing a mountain, you prepare and prepare,” Dr. June Raine, the agency’s chief executive, said on Wednesday. “We started that in June.”

When early results arrived on Nov. 10, she said, “We were at base camp.” And later, she said, “When we got the final analysis, we were ready for that last sprint.”

What about the rest of Europe?

Britain broke from the European Union’s regulatory orbit to approve a vaccine early, owing to emergency powers that the bloc gives countries in the case of a pandemic. Once Britain consummates its split from the European Union on Dec. 31, those powers to approve vaccines on its own will become permanent.

The countries that remain in the European Union are waiting for its regulator, the European Medicines Agency, to authorize a vaccine. Like the F.D.A., the European regulator has scheduled a Dec. 29 meeting to consult outside experts and offer an opinion on the Pfizer vaccine.

The agency’s job is complicated by its obligation to solicit the views of all 27 E.U. countries. That process has been accelerated during the pandemic, but it will still take several days for countries to weigh in after the meeting, which is likely to delay vaccinations until early January.

When will the first doses arrive in Britain?

Pfizer plans to ship 800,000 doses to Britain in the coming days. Starting Tuesday night, those doses were being prepared for shipping at a factory in Puurs, Belgium, BioNTech said.

The doses will be packaged in boxes, with dry ice keeping them at the South Pole-like temperatures they require, before they are put on trucks or planes and taken to Britain. They will arrive in government distribution warehouses by the weekend, Pfizer said on Wednesday.

British hospitals have already begun emailing staff members to schedule vaccinations, with a London hospital system indicating that its first doses will be given at 7 a.m. on Monday. Britain placed advance orders for 40 million doses of the Pfizer vaccine but most of those are expected to be administered next year. Each patient needs two, a month apart.

Who will be vaccinated first in Britain?

A government advisory body released its list of vaccine priority groups on Wednesday. At the top of the list are nursing home residents and workers, followed by people older than 80 and health and social care workers.

The National Health Service has roughly 150,000 doctors and more than 330,000 nurses and midwives.