Omicron subvariant spreads quickly across U.S.

A new coronavirus subvariant, dubbed the “stealth” version of omicron, has become dominant around the globe and is making its way across the United States. But it’s unclear whether it poses any heightened risk to Americans.

The subvariant, BA.2, was first detected in the United States in January and has quickly spread in the Northeast and the West, according to the Centers for Disease Control and Prevention. As of March 19, the variant made up about 35 percent of U.S. coronavirus cases. The week prior, the subvariant made up only 22 percent of cases.

The World Health Organization reported this week that BA.2 represented 86 percent of newly reported COVID-19 cases globally.

Medical experts refer to BA.2 as “stealth” omicron due to genetic mutations that could make the subvariant difficult to distinguish from the delta variant using PCR tests. BA.2 could drag out the omicron surge in much of the world, explained the American Medical Association’s director of science, Andrea Garcia, in an February video update.

“While BA.2 does not appear to cause more severe disease and our vaccines appear to be effective, BA.2 does show signs of spreading more easily,” she said, noting that the spread could slow down the current decline in COVID-19 case counts.

Omicron has already spread more easily than the delta variant or the coronavirus strain that circulated in 2020, Garcia said, leading to daily case counts peaking in January this year. The CDC’s COVID-19 data tracker reported a rolling seven-day average of nearly 900,000 new daily cases on Jan. 13.

The World Health Organization has described BA.2 as “inherently more transmissible” than the original omicron variant, BA.1 However, more data is needed to determine if BA.2 causes illness as severe as omicron BA.1.

“BA.2 should continue to be monitored,” the organization said. “However, the global circulation of all variants is reportedly declining.”

The CDC’s COVID data tracker shows that U.S. daily cases have dropped to their lowest levels since July 2021. Alongside that, reported daily deaths this month have ranged from approximately 900 to 2,000, down from 1,200 to 2,500 during COVID-19’s January 2022 spike.

The new subvariant comes as states and jurisdictions around the country lift mask mandates and daily life returns to normalcy. Hawaii and Puerto Rico were the last state and territory to lift mask mandates and travel restrictions this month.

A preliminary study based in Qatar suggested that the Pfizer and Moderna COVID-19 vaccines protect against both the BA.1 and BA.2 subvariants. The study, which is not yet peer-reviewed, shows two doses of the Pfizer vaccine to be 70-80 percent effective at preventing hospitalization or death in the short term, and 90 percent effective with a booster shot. The Moderna shot had similar results.

Additionally, while reinfection with omicron is possible, people previously infected by BA.1 are likely to have “strong protection” against BA.2, according to WHO.

An estimated 95 percent of American adults already have COVID-19 antibodies from vaccination or prior infection, according to a December CDC study of blood donors. But the degree to which these antibodies protect against infection is unclear. While a positive antibody test can identify prior infection, the Food and Drug Administration has said more research is needed to understand if antibodies provide immunity in people who have received the COVID-19 vaccine.