Covid subvariants reflect a rapid “viral evolution”

An omicron subvariant is once again demonstrating immune-dodging abilities, posing a threat to both vaccinated and previously infected individuals.

A report published Wednesday in the New England Journal of Medicine suggests that the subvariant, called BA.4.6, could drive reinfections.

As of Friday, BA.4.6 accounted for just over 12% of new COVID cases in the U.S. BA.5, meanwhile, has been detected in nearly 68% of new cases, according to the Centers for Disease Control and Prevention.

These subvariants are far from the only strains that experts worldwide are keeping their eyes on. Other omicron subvariants that have piqued the interest — and concerns — of scientists read like a viral alphabet soup: BQ.1, BQ.1.1, BF.7. (Those three, as it turns out, each account for around 5% of new U.S. cases.)

Gone are the days of identifying COVID by Greek letters, such as alpha and delta. Ever since the omicron variant emerged, it’s been omicron all the way down, with omicron subvariants splitting off into their own subvariants.

“It’s astonishing to see how the virus keeps mutating at such a rapid rate,” said study author Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at the Beth Israel Deaconess Medical Center in Boston. “This is essentially viral evolution on steroids.”

Barouch’s study was small, including just 35 people who’d had either the COVID vaccine or an omicron infection. Most, regardless of prior infection, had at least three doses of COVID vaccine. Blood samples showed that antibodies meant to neutralize BA.4.6 were about twofold lower than antibodies for BA.5.

“This suggests that omicron continues to evolve and continues to evolve in a way that becomes more transmissible and more effective at escaping vaccines and immune responses,” he said. “The results are actually a harbinger to new variants that might be even more worrisome.”

Viruses mutate at random, but mutations that give the virus an advantage over the immune system, vaccines, or treatments tend to be the ones that stick around.

“The virus is very rapidly diversifying,” said Bill Hanage, an associate professor of epidemiology at the Harvard T.H. Chan School of Public Health.

Compounding matters further, people have different levels of protection, depending on which vaccines they got (or didn’t get) and how many infections they’ve had.

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