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New Vaccine Puzzle: Who Should Get Which Shot?

LONDON — First came the good news. The European Union authorized a third vaccine. Then, the bad news. Regulators in country after country …

LONDON — First came the good news. The European Union authorized a third vaccine.

Then, the bad news. Regulators in country after country suggested restricting it to younger people until more testing was done.

The decisions marked the start of a delicate new phase of vaccination drives, one in which a growing menu of coronavirus vaccines was accompanied by contentious debates about who should be given which shots.

Those debates are a testament to the world’s good fortune in having several strong vaccines only a year into the pandemic. But every vaccine comes with its own idiosyncrasies, including gaps in clinical trial data. And that has thrown up agonizing choices for countries already struggling to administer shots, forcing health officials to weigh their qualms about certain vaccines with the need to inoculate people before dangerous variants take hold.

After the European Union authorized the AstraZeneca-Oxford vaccine last week, adding a third shot to the bloc’s arsenal, Germany, Italy, France, Belgium, Lithuania, Poland, Austria and Sweden all said they would restrict it to younger people or were considering doing so, citing a scarcity of data on the vaccine’s efficacy in older people.

Under those plans, older people would instead be scheduled to receive the Pfizer-BioNTech or Moderna vaccines, potentially leaving them unvaccinated for a period even as younger people are inoculated with the AstraZeneca shot.

But those strategies, tangled as they may be, will at least make a new vaccine available to younger people, scientists said, a scenario far preferable to no one receiving AstraZeneca’s shot.

A volunteer receiving an AstraZeneca-Oxford shot during clinical trials last year in Britain.Credit…Andrew Testa for The New York Times

Some scientists are now urging the United States to adopt the same approach, as the country remains without an alternative to the hard-to-store Pfizer and Moderna vaccines. Its regulators refuse to authorize AstraZeneca’s shot until another clinical trial generates more data, including on how it works in older people.

In the absence of that data, targeting the vaccine to those in whom it is known to be effective was an urgently needed stopgap, scientists said — all the more so now that the virus is rapidly acquiring new and dangerous mutations.

“This is a pragmatic solution to a desperate situation,” said Dr. Peter Hotez, a vaccine scientist at the National School of Tropical Medicine at Baylor College of Medicine in Texas. “Everything’s changed. The whole Biden plan made perfect sense up until about three to four weeks ago when we realized the pace of the variants emerging, and therefore you have to adjust.”

When the British scientists behind the AstraZeneca vaccine planned large-scale clinical trials in Britain and Brazil last year, they played it safe: They chose not to vaccinate older participants until they knew the vaccine was safe in younger ones, a decision that led to fewer older people being inoculated over the course of the trials.

Britain, India and other countries authorized the vaccine for all adults anyway, relying on evidence that older people generate significant immune responses to the vaccine, an indicator that it will offer at least some protection.

But European Union health officials have been more cautious, hewing closely to the clinical trial findings as they try to ensure that no one outside the most closely-studied groups is vaccinated.

Yet, some scientists said that reserving the AstraZeneca shot for younger people would only delay injections for the people most in need of protection.

“This complicates the problem,” Walter Ricciardi, a professor of public health in Italy and an adviser to the Health Ministry, said of the plans. “What we need at the moment is to protect the most vulnerable people, which for sure is not the people younger than 55 years old.”

Confusion bubbled up in Italy after regulators there said AstraZeneca’s vaccine should, with some exceptions, “preferably” be used on adults under 55. Pfizer and Moderna’s shots, both mRNA vaccines that have shown roughly 95 percent efficacy in preventing Covid-19, should be given to the most vulnerable people, they said.

Preparation of a Pfizer-BioNTech vaccine in December in a laboratory at the Piacenza hospital in Piacenza, Italy.Credit…Alessandro Grassani for The New York Times

AstraZeneca’s vaccine had 62 percent efficacy at two full doses in clinical trials, but it protected all participants against severe illness or death.

In Italy, rumors quickly began to spread about who would receive which vaccine. News reports suggested the AstraZeneca shot would be reserved for younger essential workers, like soldiers, teachers and janitors.

But Italians spotted a hole in the plan: Some hundreds of thousands of public workers are too old to be allowed an AstraZeneca shot, but too young to qualify yet for an mRNA vaccine.

Salvatrice Alario, 65, a primary school Italian and art history teacher in Catania, Sicily, is among those who now fears that she is one of the people caught in the middle, with little chance of soon being vaccinated.

“If I could choose, I’d like to get the safest one, but more than anything, I would like to get vaccinated as soon as possible,” Ms. Alario said. “I am scared, like everyone.”

Age limits have also thrown vaccine plans into flux in Germany, where an immunization committee authorized the AstraZeneca vaccine only for adults under 65. Given the limited supplies in Germany, those shots are likely to be reserved for younger medical workers and nursing home aides.

Still, some people resisted taking AstraZeneca’s shot, rather than Pfizer’s — a sign of the way people may grow choosier as more vaccines are authorized.

And beyond the question of effectiveness was the matter of where the vaccines were made.

In England, the AstraZeneca shot has become known to many residents simply as “the English one,” making it all the more attractive. In Germany, the Pfizer shot, developed by scientists from the western city of Mainz, is spoken of with pride as “the German one.”

A waiting area inside a vaccination center in Berlin in December.Credit…Lena Mucha for The New York Times

Inge Potraz, 63, who has a pre-existing respiratory illness, said that she preferred to wait for Pfizer: “I don’t want the AstraZeneca vaccine, because I think that 70 percent or even less protection is too risky,” she said.

Scientists have largely advised people to accept the first vaccine they are offered, given the widespread protections against severe disease and the societal need to tamp down the emergence of new variants.

But for governments, questions of how to target vaccines to different groups “are never easy decisions,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University in Tennessee. American officials have not given any indication that they are considering such a plan.

So far, countries have largely tailored vaccine offerings based on where the shots can be stored and transported. The mRNA vaccines must be kept at very cold temperatures, making it difficult to reach older people in rural areas.

The AstraZeneca vaccine, which can be stored in normal refrigerators, would be a boon to older, harder-to-reach residents. But limiting it to younger people would undo those advantages.

And despite embarrassing shortages of the AstraZeneca vaccine in Europe that created a rift with the company, countries are still counting on it, all the more so because Pfizer shipments have also been smaller than expected.

The AstraZeneca vaccine.Credit…Andrew Testa for The New York Times

“What if one of these countries now has a situation where they’re running out of the mRNA vaccines — are they not going to give the elderly any vaccine?,” said Dr. Ofer Levy, director of the Boston Children’s Hospital’s Precision Vaccines Program, a project to tailor vaccines for vulnerable people.

AstraZeneca and Oxford researchers have said their data point to similar levels of protection in older and younger people. That question could be definitively answered within weeks, when AstraZeneca reports results from a late-stage clinical trial in the United States that enrolled many older people. Those findings could open the door to authorization in the United States and changes to the vaccine rollout in Europe.

Britain, for its part, has achieved one of the world’s fastest vaccination programs in part by using both the AstraZeneca and Pfizer vaccines across all adults.

Since European health officials began questioning the AstraZeneca vaccine in recent days, Judy Butler, 60, a part-time nurse in northeast England, said some people had begun switching their allegiance to the Pfizer shot, an omen of the damage that the controversy could yet do for vaccine confidence.

But affections for the homegrown AstraZeneca vaccine remain strong, especially after the company published data on Tuesday suggesting that it could reduce transmission of the virus.

Ms. Butler took it as soon as it was offered. She said her aunt, offered the Pfizer vaccine, professed to want to “wait for the English one.”

“I was cringing a bit,” Ms. Butler said. “But anyway, I think she got Pfizer. Hopefully no one told her.”

Benjamin Mueller reported from London and Rebecca Robbins from Bellingham, Wash. Reporting was contributed by Melissa Eddy from Germany and Gaia Pianigiani from Italy.

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