US health officials debate whether to change COVID vaccine for fall

U.S. health officials face a crucial decision whether to offer new COVID-19 booster shots this fall that are modified to better match recent changes in the shape-shifting coronavirus.

Moderna and Pfizer have tested updated vaccines against the super-contagious omicron variant, and Food and Drug Administration advisers will debate on Tuesday whether it’s time to make a change – paving the way for similar moves by others. other countries.

“It’s the hardest science,” FDA vaccine chief Dr. Peter Marks told The Associated Press, adding that a final decision is expected within days of the advisory group’s recommendation.

Current COVID-19 vaccines have saved millions of lives around the world in 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 these vaccines target the original coronavirus strain and between waning immunity and a relentless barrage of variants, infection protection has dropped dramatically. The challenge is to decide if modified boosters offer a good chance of mitigating another surge when there’s no way to predict which mutant will be the primary threat.

In an analysis prepared for Tuesday’s meeting, FDA officials acknowledged that the targeting of last winter’s version of omicron is “somewhat outdated” since it has already been replaced by its even more contagious relatives. .

“Obviously we’d like to do it well enough,” Marks said, so that with one more hit “we get a full season of protection.”

Many experts say that updated boosters promise at least a little more benefit.

“It’s more likely to be helpful” than just giving extra doses of today’s vaccine, said epidemiologist William Hanage of the Harvard TH Chan School of Public Health.

That’s assuming the virus isn’t throwing another curve ball.

“We’re tracking rather than moving forward, which is so vexing – that we haven’t found a better variant-proof vaccine,” said Dr. Eric Topol, director of the Scripps Research Translational Institute. , who urged a big push from the government for next-generation vaccinations.

Adding to concern over a winter surge of COVID-19, about half of Americans eligible for that all-important first booster dose have never received it. An updated version might appeal to some.

But “we have to change our expectations,” said Dr. William Moss of the Johns Hopkins Bloomberg School of Public Health, who noted that studies at the start of the pandemic raised unrealistic hopes of blocking even the mildest infections. . “Our strategy cannot be booster doses every two months, or even every six months, to prevent infections.”

The best candidates are what scientists call “bivalent” vaccines – a combination of the original vaccine and omicron protection.

This is because the original vaccines stimulate the production of at least some anti-virus antibodies strong enough to cross-react with new mutants – in addition to their proven benefits against serious diseases, the immunologist said. ‘University of Pennsylvania E. John Wherry.

“Being able to push the boost response a bit one way or the other without losing the core is really important,” he said.

Moderna and Pfizer found that their combined injections significantly increased anti-omicron antibody levels in adults who had already received three vaccines, more than just giving another regular dose.

Recipients also developed antibodies that could fight new omicron parents named BA.4 and BA.5, but not as much. It’s unclear how much protection this will translate to and for how long.

Antibodies are a key first layer of defense that forms after vaccination or prior infection. They can prevent infection by recognizing the outer coating of the coronavirus – the spike protein – and blocking it from entering your cells.

But the antibodies naturally wane, 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 the new omicron relatives are even better at dodging antibodies – both in vaccinees and in people who have recovered from the disease. original omicron.

This first booster was supposed to boost people’s immune memory, which is why protection against hospitalization and death turns out to be longer lasting. If the virus bypasses the antibodies, different defenders called T cells spring into action, attacking the infected cells to curb the disease.

“T cells recognize the virus in a fundamentally different way,” not looking for the spike protein in disguise, but for parts of the virus that haven’t been altered as much so far, Penn’s Wherry said.

Yet, as people age, all parts of their immune system gradually weaken. There are few 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 called on the FDA to stop focusing solely on antibodies and start measuring T cells when deciding vaccination strategy.

The Biden administration has made it clear that it needs Congress to provide more money so that if the FDA clears 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 increased research funding was also key to creating better next-generation vaccines, such as nasal versions. which might better block the infection in the nose or more variant resistant injections.

“The virus is changing and we have to keep up with it,” Fauci said.


The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.

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