FDA advisers consider changing COVID vaccine to attack latest omicron strain

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COVID-19 vaccines are on the way for a big prescription change this fall.

Current vaccines still contain the original strain of the coronavirus, the one that started the pandemic, though it has long since been replaced by mutated versions as the virus rapidly evolves.

On Thursday, scientific advisers to the Food and Drug Administration (FDA) reviewed whether the next round of injections in the US should only include protection against the newer variants that now dominate worldwide. world: a branch of the omicron family tree called XBB.

While infections are down, the virus could be a real concern next winter, FDA vaccine chief Dr. Peter Marks said as he began the day-long meeting.

“We are concerned that we could have another wave of COVID-19 at a time when the virus has evolved further, population immunity has declined further, and we are moving indoors for the winter,” he said.

Here are some things you should know:


The FDA told Americans to expect an updated fall vaccine against COVID-19, just like they get a new flu shot each fall. Although most of the population has been infected or received at least one round of vaccinations, the coronavirus continues to produce new strains.

What's in use in the US now are combination shots from Pfizer and Moderna that combine the parent strain with protection against last year's most common omicron variants, called BA.4 and BA.5. But only 17% of Americans rolled up their sleeves for a combined booster.

And while the FDA allowed seniors and others at high risk to get an extra booster dose this spring, most people will be many months after their last shot by fall.

Those currently available vaccines still help prevent serious illness and death, even as XBB variants have taken over. But protection gradually wanes over time and was short-lived against milder infections even before the virus inevitably evolved again.


Last year, when regulators were scrambling to decide how to update the vaccine, a combination shot seemed the safest bet. Omicron was fairly new, and there was no way of knowing how long it would last or whether the next big coronavirus shift would look more like the original strain.

Now, "there's really no reason to keep the parent strain there," said Dr. Rachel Presti, an infectious disease specialist at Washington University in St. Louis. She is not on the FDA panel.

If you do, you actually have a disadvantage called "impression". After repeated exposure to the original strain, people's immune systems tended to recognize it and respond more strongly than to half of the brand new booster dose.

Therefore, the FDA is inclined to remove the original strain and choose a fall shot recipe that targets only XBB. The hope is that the XBB variants will be different enough to trigger the immune system to produce cross-protective and more diverse virus-fighting antibodies.

Vaccine advisers from the World Health Organization and European regulators recently made similar recommendations.


Another challenge: deciding which XBB variant to target, as whatever is spreading now will likely have mutated again by winter.

Regulators will make their best guess, just as they do every year when setting the prescription for the fall flu vaccine.

The FDA has identified three XBB subtypes as the main strain options. Vaccine makers have already been developing formulations that target XBBs, and FDA outside advisers will review new data Thursday on how well those options rev up the immune system.


FDA advisors will also debate that. Older adults and others at high risk due to severely weakened immune systems continue to have the highest rates of hospitalization from COVID-19, even as cases have declined. One question is whether they will be required to receive just one vaccine or will be eligible for more than one.

Another is how many doses younger children who have never been vaccinated would need.

Ultimately, the Centers for Disease Control and Prevention will make the final recommendations.

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