The BA.5 subvariant of Omicron was estimated to make up 81.9% of the circulating coronavirus variants in the United States for the week ended July 23, the US Centres for Disease Control and Prevention (CDC) said on Tuesday.
This was higher than the 75.9% prevalence estimated in the preceding week.
BA.5 has been driving a surge of new infections globally and has shown to be particularly good at evading the immune protection afforded either by vaccination or prior infection.
Omicron subvariant BA.4 was estimated to make up 12.9% of the circulating variants in the United States, the data showed.
The US Food and Drug Administration has asked vaccine manufacturers to target the two currently dominant subvariants for a potential fall season booster dose.
US health officials are also urging people aged 50 or more to get a booster shot, adding that doing so would not prevent them from getting another "bivalent" booster designed to fend off Omicron more specifically later this year.