A new COVID-19 variant, known as XEC, is spreading across the United States and Europe, drawing attention from health officials and researchers as they monitor its growth ahead of the winter season. The variant has already been detected in at least 25 U.S. states, with New Jersey, California, and Virginia reporting the highest number of cases. Labs in these states have confirmed over 100 infections, though the exact impact of this new strain remains uncertain.
XEC has been described as a recombinant strain, meaning it results from the combination of genetic material from two closely related variants, KS.1.1 and KP.3.3. These parent strains are descendants of the JN.1 variant, which played a significant role in last year's winter surge. Recombinant strains can exhibit variations in transmissibility and resistance to immunity, which is why XEC has captured the attention of experts.
Health officials have yet to raise significant alarms over the XEC variant, especially compared to past strains that caused more concern, such as BA.2.86. According to the Centers for Disease Control and Prevention (CDC), COVID-19 trends are still relatively high but have slowed since the summer wave of infections peaked last month. While XEC is being watched closely, its emergence has not yet prompted a major shift in public health policy.
In the U.S., the majority of XEC cases have been detected through routine testing, particularly in hospital settings. For example, labs at Virginia Tech's Fralin Biomedical Research Institute identified some of the earliest cases in the country, dating back to July. However, researchers like Carla Finkielstein, head of the institute's molecular diagnostics lab, have noted that it is still too early to determine clear trends. "We do not see a particular trend. We should keep an eye on the samples coming and continue genomic screening more broadly," Finkielstein said.
Although XEC has been identified in multiple regions, experts are divided over whether it will surpass other variants currently circulating. Some argue that XEC could become the dominant strain in the U.S. by winter, while others are skeptical, pointing to the continued prevalence of the KP.3.1.1 variant, which has been dominant for several weeks. Mike Honey, an Australian variant tracker, has flagged XEC's growth in Germany, adding to the international interest in the strain. Still, it is unclear whether XEC will outcompete KP.3.1.1, which currently accounts for more than half of U.S. COVID-19 cases.
Despite XEC's rise, health officials, including UCSF infectious disease specialist Dr. Peter Chin-Hong, remain confident that the updated COVID-19 vaccines will provide protection. Chin-Hong emphasized that the vaccines were designed to address circulating variants like XEC. "This new variant that's been described in Europe is very similar in general," Chin-Hong said. He believes the updated vaccines will reduce the chances of severe illness, hospitalization, and death, particularly for vulnerable populations such as the elderly and immunocompromised.
The CDC continues to recommend that Americans receive the latest round of COVID-19 vaccines this fall and winter. These vaccines have been updated to target the KP.2 strain, which shares similarities with XEC. While some experts had initially called for targeting the JN.1 variant, the U.S. Food and Drug Administration (FDA) ultimately chose KP.2 for this season's shots. The FDA has expressed "high confidence" in the effectiveness of these vaccines, even as XEC spreads.
The emergence of the XEC variant also comes as the CDC predicts another rise in COVID-19 infections over the winter, with a peak expected in mid-January. However, there is no indication that XEC will lead to more severe outcomes than previous strains. A spokesperson for the CDC confirmed that there are no specific symptoms associated with XEC that differ from other co-circulating strains of SARS-CoV-2. "At this time, we anticipate that COVID-19 treatments and vaccines will continue to work against all circulating variants," the spokesperson said.
As the virus continues to evolve, researchers and health officials are focused on maintaining public vigilance and preparedness. While XEC may gain further ground, it serves as a reminder that new variants are a natural part of the virus's progression. Vaccines, treatments, and public health measures remain the primary tools to mitigate the impact of COVID-19, even as new strains like XEC emerge.
