Two new omicron subvariants are currently driving a new Covid-19 surge in New York, leading health officials to recommend residents take precautions, including masking, once again.

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Two new omicron subvariants are spreading

Two new subvariants—BA.2.12 and BA.2.12.1—have evolved from the original BA.2 subvariant, and they have been detected in more than 40 countries and over 30 U.S. states. In New York, these subvariants are driving a new surge, where they accounted for 70% of new cases in March, largely in the state's central region.

According to the New York State Department of Health (NYSDH), the two subvariants are believed to be around 23% to 27% more transmissible than the original BA.2 subvariant, although it is not clear whether they lead to more severe disease.

Separately, Cornelius Roemer, a computational biologist, believes the two subvariants may have advantages that could help it spread more quickly and infect people more easily. In particular, the BA.2.12 subvariant appears to have a 30% to 90% growth advantage per week over BA.2, and BA.2.12.1 has a mutation that helps evade immunity and infect cells more easily.

Although the number of new cases in New York is still far below those seen during the earlier omicron wave, the state is "essentially back at levels of case rates back to the Delta wave," said Eli Rosenberg, deputy director of science at NYSDH. "This would have been a very significant wave already by last year's standards."

As cases surge in New York, health officials urge precautions

According to CDC guidelines, people are recommended to wear masks if they live in areas with high Covid-19 risk, which is determined by a combination of case rates, hospitalizations, and hospital capacity. Of the 14 counties nationwide currently labeled as "high" risk, 10 of them are in New York state.

"[The surge in New York is] just a reminder that we're not out of the woods with regard to this virus, and people should continue to take precautions and to get fully vaccinated if they haven't completed their course," said Kirsten St. George, a NYSDH virologist who led the state's research into the subvariants.

As cases continue to rise across New York, state health officials have recommended several precautions for residents, including:

• Getting fully vaccinated and boosted when eligible
• Wearing a mask in public indoor spaces, regardless of vaccination status
• Getting tested after exposure, symptoms, or travel
• If testing positive, staying home and consulting with a health care provider
• Improving air ventilation or gathering outdoors for social events to reduce transmission

"While these subvariants are new, the tools to combat them are not," said New York Health Commissioner Mary Bassett.

Will the BA.2 subvariants lead to a new surge nationwide?

So far, the rise in cases due to BA.2, the original and all of its subvariants, has been much slower and more gradual than the sharp spike seen with the original omicron variant BA.1, and many health experts do not expect cases to surge to the same levels as those during the omicron wave.

According to Ali Mokdad, a professor of health metrics sciences at the University of Washington, population immunity built up by vaccination and prior infections will likely protect the United States from another large surge even if cases continue to rise.

"We're going to have some infections here and there, but it's not going to shut down the country," Mokdad said. "Life has to go on. We have to be vaccinated and boosted. We need to protect the vulnerable, but we have to get used to it."

In addition, experts said they expect Covid-19 vaccines to remain protective against the different BA.2 subvariants, at least when it comes to severe illness and hospitalization.

"I'm relatively optimistic that, despite all of these changes in the virus, the vaccines will hold up," said Jeremy Luban, a virologist at UMass Chan Medical School. "So people who have been vaccinated and boosted are not going to be hospitalized, by and large, unless there's some extenuating circumstances." (Doucleff, "Goats and Soda," NPR, 4/14; Mandavilli, New York Times, 4/13; Sullivan, The Hill, 4/13; Lee, Forbes, 4/15; Gleeson, USA Today, 4/14; Herbert, Syracuse.com, 4/15)