How worried should we be about the new BA.2 Omicron subtype? Here's what we know

·3 min read
Jeffrey Toth, RN, administers a coronavirus PCR test
Marshall Ted Lingad, 18, has his nose swabbed for a COVID-19 test by registered nurse Jeffrey Toth outside Arrowhead Regional Medical Center in Colton on Jan. 11. (Irfan Khan / Los Angeles Times)

California has identified a number of cases of BA.2, a sublineage of the Omicron variant of the coronavirus that's gaining more attention.

Four cases of BA.2 have been identified in Los Angeles County and two in Santa Clara County, Northern California's most populous county.

Is BA.2 seen as a potential cause for concern?

The World Health Organization has said the appearance of the subtype BA.2 is increasing in many countries. Denmark, for example, has seen substantial growth of BA.2.

It's different from BA.1, which accounts for the vast majority of Omicron cases to date, according to the WHO.

"Investigations into the characteristics of BA.2, including immune escape properties and virulence, should be prioritized independently (and comparatively) to BA.1," the WHO said.

What are L.A. County health officials saying about BA.2?

L.A. County Public Health Director Barbara Ferrer said Thursday that epidemiologists have noticed the BA.2 sublineage of Omicron is spreading slightly faster in some countries than other mutations of Omicron.

"We don't yet know how BA.2 might be different from other Omicron lineages. And scientists will be working rapidly in the coming weeks to learn more about immune evasion, severity and transmissibility," Ferrer said.

Is BA.2 causing a new surge in some places?

"In places that have already passed their peak of Omicron cases, it does appear that BA.2 is causing a new surge," Ferrer said.

Will current vaccines be less effective against BA.2 than the main Omicron subtype?

It actually does not appear that BA.2 acts dramatically differently from other Omicron sublineages, at least among places at the peak of their Omicron surge that have significant BA.2 prevalence, Ferrer said.

"And compared with other Omicron lineages, BA.2 does not really have many unique mutations that would be impacting the part of the virus that's targeted by our immune system," Ferrer said.

Can someone who has been infected with the main Omicron subtype be reinfected with BA.2?

That's an unanswered question. Ferrer said she hopes surviving an infection of the main Omicron subtype will keep a person immune to being reinfected with BA.2, but the answer is not available yet.

Will BA.2 result in another jump in coronavirus cases in L.A. County?

Because BA.2 can spread widely, that's the big concern.

"We're not at a low enough place, with low enough transmission, for us not to continue to be sensible about precautions," Ferrer said. "And my hope is that people do continue to be sensible as we get more information about BA.2."

According to a Times analysis of state data released Thursday, reflecting numbers reported through Wednesday, L.A. County is averaging about 29,000 new coronavirus cases a day over the past week, down 34% from the Omicron peak of 44,000 cases a day a couple of weeks ago but still nearly twice as high as last winter’s peak of 16,000 cases a day.

This story originally appeared in Los Angeles Times.

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