Oh, no *another* new variant?! What do we know about BA.2.86?

COVID Variants Infectious Diseases

A: Once again, we’re in watchful waiting mode. We’ve got eyes on BA.2.86 because it is “highly mutated” compared to other variants currently circulating. But it’s currently at very low levels and could fizzle out—it’s too soon to tell.

BA.2.86 is still an Omicron offspring, but it’s getting attention because it has more than 35 mutations in the spike protein compared with XBB.1.5, the dominant variant during most of 2023. This is as big as the difference between the Omicron variant and the Delta variant that preceded it. Only a handful of samples of BA.2.86 have been identified, including 2 in the US. But because it has shown up in several countries, it’s safe to assume it is circulating more broadly.

The key concerns with any new variant, and what we know:

➡️ Immunity: The main concern is that with this many mutations, current antibodies from vaccination or previous infection may not be a good match. This could mean a higher chance of infection, but protection against severe disease should be more durable.

➡️ Transmissibility: A new variant could be more transmissible because immune escape makes new infections easier (see above). And/or–a mutation could make the variant “intrinsically” more transmissible by latching on to our cells better or making more copies of itself in our noses, etc. It’s too early to know this about BA.2.86.

➡️ Severity: This variant is brand new, so we have no data to suggest either way that this variant is more or less severe. This is something we always keep an eye on. But with the increases in population immunity over the last 3+ years, “effective” severity has declined even if the “intrinsic” severity of the virus stays the same. So it’s unlikely (but not impossible) that we would see dramatically worse outcomes with a new variant.

➡️ Treatment: The mutations in this variant don’t change the effectiveness of Paxlovid or other antiviral treatments.

➡️ Testing: The variant can still be detected by rapid antigen or PCR testing (these tests target a different part of the virus that doesn’t change as much, not the spike protein).

➡️ Vaccines: The updated boosters (coming soon!) are a good match for the currently dominant circulating XBB subvariants including EG.5 (“Eris”) and FL.1.5.1. *If* BA.2.86 were to become dominant over the next few months, they could be less effective for protection against infection, but still likely excellent for protection from serious disease.

➡️ Primary Prevention: As always, new variants don’t defy the laws of physics. Stay home when you are sick. Test yourself if you have symptoms. Wear a mask in crowded indoor spaces and when sick. Mind that ventilation.


BA.2.86 is currently a “variant under monitoring” because of its high number of mutations. It has only been found in a handful of cases, with no evidence (yet) that it is growing in prevalence. In the past, some variants with concerning mutations have died out without becoming dominant—a lot is due to random chance.

It’s too soon to tell if BA.2.86 is the next “Omicron” in the sense of taking a big evolutionary leap and taking over from other variants. It could be, or it could be a big nothing. Those Nerdy Girls will keep you posted.

In the mean time, the US CDC has just started a new weekly update on respiratory viruses—the first edition covers their risk assessment of BA.2.86 and gives an excellent summary.

Stay Safe, Stay Well.

Those Nerdy Girls

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