The World Health Organization says the Omicron XBB.1.5 subvariant of the coronavirus may be more transmissible and highly immune evasive.
The WHO published its rapid risk assessment by experts on the XBB.1.5 variant on Wednesday.
The report says the subvariant has shown relatively high growth advantage in the United States and appears to be one of the most antibody-resistant variants to date.
It says, "There is currently no data on real world vaccine effectiveness against severe disease or death."
The report also says, "XBB.1.5 may contribute to increases in case incidence globally," but "the overall confidence in the assessment is low as growth advantage estimates are only from one country," the United States.
The US Centers for Disease Control and Prevention says the XBB.1.5 subvariant made up an estimated 27.6 percent of all new infections in the country during the week through last Saturday. That's a significant increase from the estimated 2.3 percent as of December 3.
The WHO says XBB.1.5 cases were reported by 38 countries from October 22 last year to Wednesday. It says more than 80 percent of them were confirmed in the United States.