A pair of immune-evading Omicron subvariants are now dominant in the U.S., having overtaken so-called "stealth Omicron" and close relative BA.2.12.1 in mere weeks, according to federal health data released Tuesday.
BA.4 and BA.5, which swept South Africa this spring along thanks to their ability to evade immunity, were estimated to have caused slightly more than half (52%) of COVID infections in the U.S. last week, according to new data from the U.S. Centers for Disease Control and Prevention.
“The Omicron subvariant BA.5 is the worst version of the virus that we’ve seen,”
Dr. Eric Topol, a professor of molecular medicine at Scripps Research and founder and director of the Scripps Research Translational Institute,
wrote Monday in anticipation of the viral coup.
"It takes immune escape, already extensive, to the next level, and, as a function of that, enhanced transmissibility," well beyond what has been seen before, he wrote. "You could say it’s not so bad because there hasn’t been a marked rise in hospitalizations and deaths as we saw with Omicron, but that’s only because we had such a striking adverse impact from Omicron, for which there is at least some cross-immunity."
BA.2.12.1, another Omicron subvariant dominant before the advent of BA.4 and BA.5, was responsible for 42% of cases. So-called stealth Omicron, BA.2, nicknamed for its ability to evade detection on PCR tests, came in third, comprising nearly 6% of cases. It had been dominant in the U.S. until BA.2.12.1 overtook it last month.
The jury is still out on whether current vaccines hold up against BA.5. But given that vaccines experienced an approximate 15% drop in protection against severe disease from Delta to Omicron, "it would not be at all surprising to me to see further decline of protection against hospitalizations and deaths," Topol wrote.
. Seriously here in Brisbane, it has led to a third wave and Omicron 4 and 5 are expected to be the dominant strains in 3 weeks - they already are rising fast.