FDA picks a new strain for fall Covid vaccines. Here's what it means for your next shot.

The FDA picked the LP.8.1 Covid strain for the fall vaccines, fueling concerns that the shots may be limited to only the most at-risk Americans this fall.

The Food and Drug Administration said late Thursday it would like drugmakers to update the Covid vaccines to target the LP.8.1 strain, fueling concerns that the shots may be limited to only the most at-risk Americans this fall.

The FDA’s decision differs slightly from the recommendation made by its vaccine advisory committee earlier that day, which was to stick to the strains used in the current Covid shots, although panel members said LP.8.1 was a suitable alternative.

Studies by Moderna and Pfizer showed that an LP.8.1-targeted vaccine in fact induced a modestly stronger immune response to the circulating strains than the current Covid shots, which target a variant called JN.1 or one of its descendants, KP.2.

LP.8.1 is also a descendent of JN.1, and it is the dominant strain circulating in the U.S., accounting for roughly 3 in 4 new Covid cases, according to FDA briefing documents released earlier this week. It’s different from a strain dubbed NB.1.8.1 that was recently detected in the U.S. and caused a surge in hospitalizations in China.

Normally, changing the strain for the vaccine wouldn’t raise questions — it's been the practice of the U.S. in recent years, following a similar model to how the flu shot is updated each year. For Pfizer and Moderna, their mRNA technology makes it particularly easy to update their vaccines.