WASHINGTON (AP) — Government advisers Wednesday said it's time to update the recipe for the COVID-19 vaccines Americans will receive in the fall -- targeting a version of the ever-evolving coronavirus called JN.1.

While COVID-19 cases currently are low, more surges are inevitable and manufacturers need time to brew shots for fall. Moderna, Pfizer and Novavax all have tested doses updated to match the JN.1 variant that became dominant last winter.

But just a few months later, numerous offshoots of JN.1 already are on the rise, prompting Moderna and Pfizer to also test a slightly different vaccine formula targeting what's now the most common U.S. subtype, called KP.2.

That made for a tough choice as the Food and Drug Administration decides the final recipe. FDA's advisers voted Wednesday that the next vaccine should come from the JN.1 "lineage" or family. Then FDA vaccine chief Dr. Peter Marks challenged them to be more specific about exactly which variant to target, wondering if KP.2 was a better option.

"If this evolves further in the fall, will we regret not having been a little bit closer?" Marks said, likening the choice to how he always picks the "freshest" milk with the longest expiration date in the grocery store.

But KP.2 isn't likely to still be the biggest threat by fall, the panel responded. Having to make the choice now, they preferred the parent JN.1 variant itself rather than trying to predict which of its descendants was most likely to increase in the coming months.

"Having a vaccine that's the trunk of the tree rather than the branches makes sense to me," because it would offer some cross-protection to other subvariants that emerge, said one adviser, Dr. Melinda Wharton of the Centers for Disease Control and Prevention.

Health officials have told Americans to expect a yearly update to COVID-19 vaccines, just like they get a new flu shot each fall designed to match as best as possible the currently spreading strains. Even though just about everyone has either been infected or had at least one round of COVID-19 vaccinations, the coronavirus keeps churning out new varieties that can dodge prior immunity -– and protection also wanes over time.

Last fall's COVID-19 vaccine targeted a completely different section of the coronavirus family tree, and CDC data shows only about 22.5% of adults and 14% of children received it. But even though public concern about COVID-19 has waned, it remains deadlier than the flu, according to a recent analysis of Veterans Affairs hospitalizations this past winter.

Moderna, Pfizer and Novavax all said they could have supplies of JN.1-specific shots ready by fall, although they didn't provide amounts. Like it has in previous years, the CDC will make recommendations on who should receive updated shots and when.

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