Britain gave emergency authorization on Wednesday to Pfizer’s coronavirus vaccine, leaping ahead of the United States to become the first Western country to allow mass inoculations against a disease that has killed more than 1.4 million people worldwide.
The decision kicked off a vaccination campaign with little precedent in modern medicine, encompassing not only ultracold dry ice and trays of glass vials but also a crusade against anti-vaccine misinformation.
No country until Wednesday had authorized a fully tested coronavirus vaccine; Russia and China approved vaccines without waiting for large-scale efficacy tests.
“Help is on its way with this vaccine — and we can now say that with certainty, rather than with all the caveats,” the British health secretary, Matt Hancock, said on Wednesday, as the government exulted in its decision.
While the go-ahead bodes well for Britain, which broke from the European Union’s regulatory orbit to approve the shot early, it will have no effect on the distribution of the hundreds of millions of doses that other wealthy countries have procured in prepaid contracts.
It also offers little relief to poorer countries that could not afford to buy supplies in advance and may struggle to pay for both the vaccines and the exceptional demands of distributing them.
The Pfizer vaccine, developed with BioNTech, a smaller German firm, must be transported at South Pole-like temperatures, a requirement that could dictate who will be vaccinated first in Britain: Nursing-home residents are the top priority under advisory committee plans released on Wednesday, but officials have indicated that efforts to limit transportation of the vaccine and keep it cold may mean that National Health Service workers on the front lines will receive shots first.
The government said on Wednesday that 800,000 doses would be available by next week for health workers to begin administering, part of an enormous distribution effort involving primary care doctors and mass vaccination centers being set up by the military.
For Britain, which has suffered one of Europe’s highest per capita death tolls from the virus, the decision by its drug regulator was the latest evidence of a vaccination strategy that has been the most aggressive in the West.
After the government strengthened an old law that allows Britain to step out from under the European Union’s regulatory umbrella in public health emergencies, its Medicines and Healthcare Products Regulatory Agency fast-tracked a review of the Pfizer vaccine.
Britain has pre-ordered 40 million doses of the vaccine, which was 95 percent effective in a late-stage clinical trial. It is part of a catalog of different vaccines that the government has ordered — in all, more than five doses for each person in the country.
Prime Minister Boris Johnson’s government, battered by its handling of the pandemic, cast the authorization as a sign of Britain leading “humanity’s charge against this disease.” But the speedy approval also fed concerns about the opening of a new, politicized contest among countries to authorize vaccines quickly so that they can claim the first shipments.
While American regulators pore over raw data from vaccine makers to validate trial results, their counterparts in Britain and elsewhere in Europe lean more heavily on companies’ own analyses. Still, the British regulators’ decisions are seen as globally influential, and its analysts examine not only trial results but also manufacturing processes and controls.
British regulators are also vetting a vaccine developed by AstraZeneca, a British-Swedish company, and the University of Oxford that is cheaper and easier to store than Pfizer’s. Much of the world could rely on it, but its regulatory path forward in the United States is unclear after scientists and industry analysts questioned promising early results.
The chemistry underlying Pfizer’s vaccine had never before produced an approved shot, though the same class of vaccines has long been tested for other uses. In order to coax cells to make a viral protein, called spike, and elicit an immune response, the vaccine delivers genetic instructions, known as messenger RNA, encased in tiny fat globules.
BioNTech made a prophetic bet on the technology and joined forces with Pfizer, one of the world’s largest drug companies; they ended up delivering stunning results, on a timeline that was unheard-of before this year.
“The emergency use authorization in the U.K. will mark the first time citizens outside of the trials will have the opportunity to be immunized against Covid-19,” said Dr. Ugur Sahin, the chief executive and co-founder of BioNTech.
The U.S. Food and Drug Administration plans to decide on emergency authorization for the Pfizer vaccine shortly after a meeting of an advisory panel on Dec. 10. American officials have said vaccinations could begin within 24 hours after approval.
Another American company, Moderna, whose messenger RNA vaccine proved extraordinarily effective in large trials, said it would also apply to the F.D.A. for emergency authorization. If granted, it could go into use as early as Dec. 21, the company has said.
Britain’s power to approve vaccines before the European Union, which has its own drug regulator, applies for now only on an emergency basis. But it will become permanent after Britain consummates its split from the bloc on Dec. 31, making the speed of the Pfizer approval an early sign in the eyes of the government of the flexibility it will have once the country fully untethers itself from the rest of Europe.
Yet, Brexit has also exacted costs, starving Britain’s drug regulator of money it used to draw from contracts with the European Union.
The European Medicines Agency, which regulates vaccines across the European Union, is expected to make a decision about the Pfizer vaccine later in December. Like the F.D.A., the European Medicines Agency has scheduled a high-profile meeting with outside experts before approval.
Pfizer has said it expects to be able to produce up to 50 million doses this year, about half of them going to the United States. Since each person needs two doses, a month apart, up to 25 million people worldwide could begin vaccination before 2021.
The United States has bought 100 million doses in advance from Pfizer, and the European Union 200 million doses.
The approval arrived at a perilous moment in the pandemic in Britain, where the virus has killed nearly 70,000 people, and hundreds more each day. A third of England’s hospital systems were caring for more Covid-19 patients in recent weeks than in the spring. Several intensive care units in central England were struggling to maintain emergency care.
And while a monthlong shutdown of restaurants and pubs has stanched the spread of the virus, it is being replaced by a new system of localized restrictions, with an allowance for Christmastime travel that scientists fear will seed another uptick in infections.
In a clinical trial, the Pfizer-BioNTech vaccine proved effective among older adults, who are more vulnerable to developing severe Covid-19 and who do not respond strongly to some types of vaccines. It caused no serious side effects.
With Moderna’s vaccine unlikely to be available in Britain until at least the spring, the government has not formally requested that it undergo an emergency assessment.
As vaccines become widely available, the scientific feat of developing them will give way to the social and political problem of convincing people to take them. In Britain, the source of some of the most virulent modern disinformation about vaccines, just over half of people have said in surveys that they would definitely accept a coronavirus inoculation.
Safety concerns have only been accentuated by the speed with which vaccines have headed toward approval, despite Britain’s regulators saying repeatedly that they were not taking shortcuts.
Beyond those challenges, manufacturers will quickly need to make hundreds of millions — eventually billions — of doses of the vaccine and move them to hospitals, clinics and pharmacies without jeopardizing what is inside.
The Pfizer vaccine makes this effort especially complex. It has to be stored at around minus 70 degrees Celsius (minus 94 Fahrenheit) until shortly before it is injected, requiring transportation in boxes stuffed with dry ice. Moderna’s vaccine needs to be frozen, too, but only at minus 20 Celsius.
Those requirements, along with high costs, could substantially limit the number of countries and people that have access to those vaccines.