By LAURAN NEERGAARD, AP Medical Writer
U.S. health authorities are faced with a critical decision: to offer new booster vaccines against COVID-19 this fall that have been modified to better accommodate the recent changes in the shape-shifting coronavirus.
Moderna and Pfizer have tested updated injections against the super-contagious omicron variant, and Food and Drug Administration advisers will debate Tuesday whether it’s time to make a change, setting the stage for similar moves in other countries.
“This is science at its finest,” FDA vaccine chief Dr. Peter Marks told The Associated Press, adding that a final decision is expected within days of the advisory panel’s recommendation.
Current COVID-19 vaccines saved millions of lives around the world in just their first year of use. And injections from Moderna and Pfizer still offer strong protection against the worst outcomes (severe illness and death), especially after a booster dose.
But those vaccines target the original strain of the coronavirus, and between waning immunity and a relentless barrage of variants, protection against infection has been markedly reduced. The challenge is deciding if modded reinforcements offer a good chance of mitigating another wave when there’s no way to predict which mutant will be the main threat.
In an analysis prepared for Tuesday’s meeting, FDA officials acknowledged that targeting last winter’s version of omicron is “somewhat outdated” as it has been superseded by its even more contagious relatives.
“Obviously we’d like to do well enough,” Marks said, that with one more chance “we’ll have a full season of protection.”
Many experts say that the updated boosters promise at least a little more benefit.
“It’s more likely to be helpful” than simply giving additional doses of the current vaccine, said epidemiologist William Hanage of the Harvard TH Chan School of Public Health.
That’s assuming the virus doesn’t throw another curveball.
“We’re following rather than moving forward, which is so upsetting, that we haven’t found a better variant-tested vaccine,” said Dr. Eric Topol, director of the Scripps Translational Research Institute, who urged a major government push. for next generation immunizations.
Adding to concerns about a winter wave of COVID-19, about half of Americans eligible for that first booster dose never received it. An updated version might attract some of them.
But “we need to change our expectations,” said Dr. William Moss of the Johns Hopkins Bloomberg School of Public Health, noting that studies early in the pandemic raised unrealistic hopes of blocking even milder infections. “Our strategy cannot be booster doses every two months, even every six months, to prevent infection.”
The leading candidates are what scientists call “bivalent” injections, a combination of the original vaccine plus omicron protection.
That’s because the original vaccines stimulate the production of at least some virus-fighting antibodies strong enough to cross-react with newer mutants, in addition to their proven benefits against serious diseases, said the University of Pennsylvania, E. John Wherry.
“Being able to push the boost response a little bit in one direction or another without losing the core is really important,” he said.
Moderna and Pfizer found that their combined injections substantially increased levels of anti-omicron antibodies in adults who had already received three vaccines, more than simply giving another regular dose.
The recipients also developed antibodies that could fight omicron’s newer relatives called BA.4 and BA.5, though not as many. It’s unclear how much protection that will translate into and for how long.
Antibodies are a key first layer of defense that forms after vaccination or previous infection. They can prevent infection by recognizing the outer coating of the coronavirus, the spike protein, and blocking it from entering your cells.
But antibodies naturally decline, and each new variant comes with a different-looking spike protein, giving it a better chance of evading detection by the remaining antibodies. Separate studies published this month in Nature and the New England Journal of Medicine show that omicron’s newer relatives are even better at dodging antibodies, both in those vaccinated and in people who recovered from the original omicron.
People with that first boost were supposed to get a strengthened immune memory, which helps explain why the protection against hospitalization and death is proving longer lasting. If the virus escapes the antibodies, different defenders called T cells spring into action and attack the infected cells to stop the disease.
“T cells recognize the virus in a fundamentally different way,” not looking for disguised spike proteins but for parts of the virus that have so far not been altered that much, Penn’s Wherry said.
Still, as people age, all parts of their immune system gradually weaken. There is little data on how long T-cell protection against COVID-19 lasts or how it varies with different mutations or vaccines.
Wherry and dozens of other scientists recently asked the FDA to stop focusing solely on antibodies and start measuring T cells as it decides on a vaccination strategy.
The Biden administration has made it clear that it needs Congress to provide more money so that if the FDA approves the updated boosters, the government can buy enough for every American who wants one. And Dr. Anthony Fauci, the government’s top infectious disease expert, told Congress last week that more research funding is also critical to creating better next-generation vaccines, such as nasal versions that could better block infection in the nose or more variant-proof injections.
“The virus is changing and we have to keep up with it,” Fauci said.
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