The newer and most contagious Omicron subvariants, known as BA.4 and BA.5, now made up over 70 per cent of Covid-19 infections in the US, according to latest data released by the Centers for Disease Control and Prevention (CDC).
The BA.5 subvariant accounted for 53.6 per cent of new infections in the latest week ending July 2, while BA.4 accounted for 16.5 per cent of the new infections, Xinhua news agency reported, citing the CDC data.
BA.5 has become the dominant variant in the US.
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.