The BA.5 subvariant accounted for 53.6 percent of new infections in the latest week ending July 2, while BA.4 accounted for 16.5 percent of the new infections, CDC data showed, Xinhua reported.
BA.5 has become the dominant variant in the United States.
Health experts said the newer variants are more contagious and may pose a severe threat to immune protection.
They stressed that current public health tools are still very effective against BA.4 and BA.5, including masking indoors, avoiding crowds and getting booster shots.