A sublineage of the delta variant that has gained some traction in the U.K. has been detected in the U.S., the CDC said Oct. 21.
AY.4.2, a descendant of the highly transmissible delta variant, is on an "increasing trajectory" in the U.K., according to a recent update from the U.K. Health Security Agency. It accounted for 6 percent of all samples sequenced in the country for the week beginning Sept. 27, the most recent week with complete sequencing data.
The strain is rare in the U.S. and accounts for "well below 0.05 percent" of cases sequenced, the CDC told Becker's in an Oct. 21 statement.
"At this time, there is no evidence that the sublineage AY.4.2 impacts the effectiveness of our current vaccines or therapeutics," the agency said. "Vaccination remains the best public health measure to slow the spread of the virus and reduce the likelihood of new variants to emerge."
The variant includes two mutations on the spike protein, A222V and Y145H.
It's uncertain whether the delta relative is more transmissible, and health officials are closely monitoring it.
"The AY.4.2 is being closely monitored in the U.K. and elsewhere," Francois Balloux, PhD, director of the University College London Genetics Institute, said Oct. 18.
"It remains rare outside the U.K. There have only been three cases detected in the U.S. so far. In Denmark, the other country that besides the U.K. has excellent genomic surveillance in place, it reached a 2 percent frequency but has gone down since. In addition, functional work is underway to test whether it may be well recognized by antibodies," Dr. Balloux said.