(NewsNation) — Another COVID-19 variant is on the rise this fall, hot on the heels of a massive summer surge of the virus.

The variant, called XEC, is appearing worldwide. The SARS-CoV-2 virus mutation has also been spotted in at least half of the United States, according to preliminary numbers from the Global Initiative on Sharing All Influenza Data.

GISAID charts around 100 sequences of XEC in the U.S. in at least 25 states, with more than 800 sequences showing up in 28 countries across multiple continents.

XEC COVID-19 variant

Dr. Albert Ko, an infectious disease physician and Yale School of Public Health professor, told “TODAY” the new variant is a recombinant of two other variants: KP.3.3 and KS.1.1.

“When a person’s infected with two different SARS-CoV-2 variants, you can get what we call a recombination, where pieces of the genetic material from one recombine with the other, and that can create a new strain,” he told the outlet. 

XEC is also an offshoot of omicron, the widely spread variant that formed in 2021. According to experts, it has some of omicron’s features, too — like less severe symptoms and easy transmissibility.

“CDC is not aware of any specific symptoms associated with XEC or any other co-circulating SARS-CoV-2 lineage,” a spokesperson for the agency said in a statement to CBS.

“At this juncture, the XEC variant appears to be the most likely one to get legs next,” Dr. Eric Topol, director of the Scripps Research Translational Institute, shared on X.

His post was in response to a chart from Australian data scientist Mike Honey, who cites XEC’s first reports to Berlin, Germany, in late June. According to Honey’s data, the strain is spreading rapidly in Denmark, Germany, the United Kingdom and the Netherlands.

Is COVID-19 vaccine effective against XEC?

William Schaffner at Vanderbilt University Medical Center in Tennessee told NewScientist the newest round of vaccines should offer some protection against XEC, as they are formulated to fight omicron subvariants.

The most recent COVID-19 vaccines from Moderna and Pfizer were approved by the FDA on Aug. 24, with the CDC recommending Americans get their updated shots ahead of the winter virus season.

Amesh Adalja, infectious disease specialist and senior scholar at Johns Hopkins Center for Health Security, told NewsNation in late August that the vaccines should offer an updated level of protection.

“These new vaccines are matched to the variants, so this is likely to give you more protection than the prior vaccine, and certainly for those individuals who are at higher risk, it’s going to provide protection against serious illness, hospitalization and death,” Adalja said on “Morning in America.”