BQ.1, BQ.1.1 push BA.5 out as the dominant omicron subvariant in U.S.

The COVID-19 omicron subvariants BQ.1 and BQ.1.1 have pushed the BA.5 subvariant out of its place as the dominant version of the coronavirus in the U.S., eliciting concerns from health experts as vaccine booster uptake remains low and evidence emerges of treatments being less effective.

As of this week, the BA.5 omicron subvariant now accounts for about a quarter of new COVID-19 cases in the U.S., with BQ.1 and BQ.1.1 each making up roughly an equal proportion of infections. These two subvariants are themselves descended of BA.5 and now account for about 48 percent of cases.

For much of 2022, the BA.5 and BA.4 omicron subvariants were the predominant versions of coronavirus infections. However, the COVID-19 virus continues to mutate, resulting in pathogens that appear to be less susceptible to monoclonal antibodies.

Earlier this month, the Food and Drug Administration (FDA) updated its guidance for the monoclonal antibody bebtelovimab to indicate that BQ.1 and BQ.1.1 showed significant reductions in susceptibility to the treatment.

The FDA similarly revised its guidance for Evusheld, a combination of two monoclonal antibodies, to note significant reduction in susceptibility when it came to BQ.1 and BQ.1.1. This treatment has largely been used for those with compromised immune systems who may not develop a strong enough response after vaccination.

Other treatments, like the Pfizer antiviral Paxlovid, are expected to still be effective against these newer subvariants, as the drug inhibits a specific enzyme that the COVID-19 virus needs to replicate.

Recent data has indicated that the bivalent COVID-19 booster should also still be effective against the newest variants, as the updated shot was designed to specifically build up immunity against BA.5.

Pfizer and BioNTech on Friday said their updated bivalent shot had been found to offer protection against multiple descendants of BA.4 and BA.5 in a preprint study. After a dose of the bivalent shot was administered, the companies said neutralizing antibodies against BQ.1.1 rose by 6.7-fold.

Enthusiasm for the booster has been low, however, with only about 11 percent of eligible individuals opting to get the shot so far. Case rates for coronavirus have plateaued in recent weeks after having fallen for several months.