Yes, BA.2, or ‘stealth’ omicron, subvariant is now dominant in the U.S.

Multiple news reports are attributing a surge in COVID-19 cases in some countries to the omicron subvariant BA.2. It’s often informally referred to as “stealth" omicron because it has genetic mutations that could make it more difficult to distinguish from the delta variant through testing.

Some medical experts are worried about another potential uptick in U.S. COVID-19 cases as news headlines claim the omicron subvariant has become dominant.

THE QUESTION

Has BA.2, or “stealth” omicron, become dominant in the U.S.?

THE SOURCES

• Jen Psaki, White House Press Secretary
• U.S. Centers for Disease Control and Prevention (CDC)
• Washington State Department of Health
• New York State Department of Health
• World Health Organization (WHO)
• Rochelle Walensky, M.D., CDC Director 
• Payal Kohli, M.D., assistant clinical professor of medicine at University of Colorado’s Anschutz Medical Campus
• Saralyn Mark, M.D., former senior medical advisor to the White House and American Medical Women's Association COVID-19 Lead
• Ali Mokdad, Ph.D., professor of health metrics sciences at the University of Washington’s Institute for Health Metrics (IHME)

THE ANSWER

Yes, BA.2, or “stealth” omicron, has become dominant in the U.S.

WHAT WE FOUND

During a briefing on March 14, White House Press Secretary Jen Psaki acknowledged that BA.2 has “circulated in the United States for some time.”

From March 20-26, BA.2 accounted for nearly 55% of COVID-19 cases in the U.S., according to estimates from the Centers for Disease Control and Prevention (CDC). That’s compared to about 40% of cases attributed to BA.1, the original version of omicron. 

Two weeks earlier, from March 6-12, BA.2 accounted for an estimated 28% of U.S. cases, compared to about 61% of cases attributed to BA.1. 

Health departments in some U.S. states, including Washington and New York, are also reporting that BA.2 has become the dominant strain. 

The latest genomic sequencing of positive COVID-19 cases in Washington state shows that more than 51% were caused by the BA.2 subvariant from March 13-19. The New York State Department of Health reports that BA.2 accounted for nearly 60% of the state’s cases from March 13-26. 

The World Health Organization (WHO) said in a report on March 22 that BA.2 made up 86% of cases reported to the global public health agency between Feb. 16 and March 17.

Is BA.2 more contagious than the original version of omicron?

BA.2 appears to have a “faster growth rate” than the original version of omicron, Payal Kohli, M.D., assistant clinical professor of medicine at University of Colorado’s Anschutz Medical Campus, said. Medical experts believe BA.2 is about 1.5 times more transmissible than BA.1, Saralyn Mark, M.D., former senior medical advisor to the White House and American Medical Women's Association COVID-19 Lead, added. 

Vaccines provide the same level of protection against severe illness and hospitalization of the BA.2 subvariant compared to other variants, experts say.

“While it is slightly more transmissible than the original omicron, our vaccines work, our boosters work, and it does not indicate more severe disease than the original omicron. So those tools are going to be key in protecting ourselves and our communities against BA.2,” CDC Director Rochelle Walensky, M.D., said during a press briefing on March 23.

Will the U.S. see another surge in cases due to BA.2?

Ali Mokdad, Ph.D., professor of health metrics sciences at the University of Washington’s Institute for Health Metrics and Evaluation (IHME), said in a tweet on March 30 the U.S. has not seen a rise in cases yet and IHME is not projecting one at the national level. 

Cases in the U.S. are expected to decline until winter 2022. However, some states will likely see a “short rise” in cases as a result of the BA.2 subvariant, Mokdad said.

Kohli previously told VERIFY that she doesn’t see BA.2 as an immediate concern since many people have immunity to the virus through natural infection or vaccination following the most recent omicron surge.  

“My bigger concern for this variant is…come fall, come next winter,” Kohli said. “If it continues to be persistent and prevalent in our community, will we start to see more cases and surges occurring as a result of this?”

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