BA.2.75 (Centaurus) is still a subvariant worth watching

The CDC’s variant prevalence estimates suggest that BA.2.75 has started to spread more in the U.S. in recent weeks.

BA.2.75, a newer subvariant that evolved from BA.2, has been driving increased coronavirus transmission in some other countries recently. You might also see it referred to as “Centaurus” on social media. This lineage has yet to be identified in large numbers in the U.S., but I was inspired by a recent reader question to share what we’ve learned about it since my previous post in July.

Scientists are concerned about BA.2.75 because it has several new mutations that are distinct from BA.2, most of those in the spike protein (where the virus binds to human cells). And some preliminary research, including recent studies in the Lancet Infectious Diseases and in the New England Journal of Medicine, have found that BA.2.75 is less susceptible to neutralizing antibodies from prior infections or treatments than past variants.

This could mean people who previously caught BA.2 or other versions of Omicron could be susceptible to BA.2.75, reports Hannah Flynn in Medical News Today. Of course, more research and data are needed on the new variant. But BA.2.75 has been driving new surges in India, Nepal, and other countries—another signal that it’s worth watching.

As I noted in today’s National Numbers post, the CDC is not yet reporting BA.2.75 prevalence estimates separately from other versions of BA.2. But it has reported an increase in BA.2 overall in recent weeks, from 0.6% of new cases in the week ending August 27 to 1% in the week ending September 10. This is probably BA.2.75, given that older versions of BA.2 haven’t been competitive in the U.S. for a few months.

Helix, a COVID-19 testing company that works with the CDC and other agencies on variant surveillance, is tracking BA.2.75 separately from BA.2 on its dashboard. According to Helix’s data, original BA.2 has stayed at very low prevalence in recent weeks while BA.2.75 has risen to 1% of cases sequenced.

It’s currently unclear—as it was in July—to what extent BA.2.75 might be able to compete with BA.5 or BA.4.6, which are the main subvariants of concern spreading across the U.S. right now. But if BA.2.75 does become dominant, it will be helpful that the newly-authorized booster shots include genetic material from the original, Wuhan variant, not just BA.4 and BA.5.

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