What to Know About Omicron’s New BA.2 Variant

What to Know About Omicron’s New BA.2 Variant

With the huge Omicron surge in coronavirus cases now receding in the United States and many other countries, reports have been cropping up in many news outlets lately about a potentially worrisome new version of Omicron — a subvariant known as BA.2 — and the threats it may pose.

Here are some key things to understand about BA.2 and what we know so far.

Scientists learned soon after the Omicron variant was first detected in November that it came in three genetically distinct varieties. They focused on BA.1, because it was about 1,000 times as prevalent as BA.2 in the early going; the third subvariant was rarer still. It was BA.1 that first broke out and raced around the world, while BA.2 took longer to become significant, but both have been on scientists’ radar from the outset.

All kinds of Omicron are highly contagious, which is why Omicron swiftly crowded out earlier variants like Delta and caused an immense global surge. But preliminary studies suggest that BA.2 is even more transmissible than BA.1. It has already become the dominant form of Omicron in a few countries and is gaining ground in others. Its potentially greater transmissibility has raised some concerns that BA.2 could cause a fresh spike or could lengthen the current one, but the jury is still out on whether that is likely to happen.

A crucial feature of the Omicron surge has been that if you are infected with the variant, your odds of becoming severely ill, being hospitalized or dying are significantly lower than they were with Delta or earlier variants. The research so far, including a new study from South Africa, indicates that BA.2 is no different from BA.1 on that score.

While it is known that Omicron generally has been somewhat better than other variants at causing “breakthrough” infections of vaccinated people, the vaccines still provide substantial protection against infection and very strong protection against severe illness. Booster shots make the protection even more robust. And once again, BA.2 doesn’t seem to change any of that: British researchers recently found that vaccines were equally effective against both Omicron subvariants.

Omicron has also been somewhat better than other variants at breaking through “natural” immunity acquired from previous infections, and some concerns have been raised that BA.2 might be able to do that to people who caught BA.1 in the Omicron surge. While such reinfections have been reported, they have so far been exceedingly rare even in countries where BA.2 is now prevalent.

BA.2 was nicknamed the “stealth variant” because initially, when the challenge for researchers was to distinguish Omicron cases from those of Delta and other variants, BA.2 did not tip off its presence in positive P.C.R. test samples the way BA.1 did, through a mutation that concealed one of the three telltale coronavirus genes that the tests detect. Now that the vast majority of positive tests involve Omicron, however, the missing mutation can make BA.2 decidedly un-stealthy, standing out from BA.1 cases in P.C.R. tests.

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