New COVID Variant XEC May Outpace Others This Fall

The new COVID-19 variant XEC may overtake others in circulation to become dominant in the coming months, experts said, but will not prompt a meaningful change in symptoms or vaccine response.

So far, the CDC’s variant proportions tracker has not registered enough cases of XEC in the U.S. to report it. (The agency’s projected estimates for the 2 weeks ending in September 14 currently show KP.3.1.1 and KP.2.3 as the leading variants, with 52.7% and 12.2% of national cases, respectively.) Another estimate using data from the variant tracker GISAID has XEC at 1.11% of U.S. cases as of September 15, with around 48 sequences reported.

First detected in Germany in June, it’s been found mostly in Central Europe, representing 10% of cases, according to the U.K.’s Science Media Centre.

“XEC represents a fairly minor evolution relative to the SARS-CoV-2 diversity currently in circulation, and is not a highly derived novel variant such as those that were granted Greek letters,” like Alpha, Delta, and Omicron, Francois Balloux, PhD, a computational biologist at University College London and director of the UCL Genetics Institute, said in a Science Media Centre statement.

Experts noted that while XEC may have a small advantage in transmission, available vaccines are still likely to provide protection from serious illness.

XEC is a “recombinant variant of some of the other Omicron lineages that have been around for a while, and it does appear to be more immune evasive, giving it a transmissibility advantage in the population with the immunity that it has,” Amesh Adalja, MD, of the Johns Hopkins Center for Health Security in Baltimore, told MedPage Today. “But it doesn’t really change anything, just like the last variant didn’t change anything, or the one before that, one before that, or the one before that.”

Currently available COVID vaccines target slightly different subvariants. The updated mRNA shots aimed at KP.2 from Pfizer-BioNTech (Comirnaty) and Moderna (Spikevax), as well as Novavax’s vaccine targeting the JN.1 variant lineage, are still protective against the most serious consequences of COVID infections, experts said.

“If this becomes a dominant variant, it will decrease the efficacy against infection of the updated vaccines, but the updated vaccines will still be durable against severe disease [and] hospitalization, and that’s what is really the primary function of our current, first-generation COVID vaccines,” Adalja said.

Still, he emphasized, the rapid mutation of the virus underscores a need for a different kind of vaccine than those currently available if the goal is to protect against infection rather than just severe disease.

“The virus is always going to be mutating away from what it was in order to get more efficient at infecting individuals,” Adalja said. “So I think this really highlights the fact that a universal COVID vaccine, or some vaccine with different technologies, perhaps a nasal vaccine and using mucosal immunity, all of those things are important.”

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