The fast-spreading BA.4 and BA.5 sub-lineages of Omicron are estimated to make up a combined 70.1% of the coronavirus variants in the US as of July 2, the US Centers for Disease Control and Prevention said on Tuesday.
BA.4 and BA.5 made up 52% of US variants for the week of June 25. They were added to the World Health Organization's monitoring list in March and designated as variants of concern by the European Centre for Disease Prevention and Control.
The US Food and Drug Administration recommended last week that Covid-19 vaccine makers change the design of their booster shots beginning this fall to include components tailored to combat BA.4 and BA.5.
BA.4 made up 16.5% of the variants in circulation, the latest data showed, while BA.5 accounted for 53.6%.