Public Health

What is the BA.2 or “stealth” Omicron subvariant?


The World Health Organization (WHO) is currently monitoring the original Omicron variant, BA.1, along with several additional subvariants BA.1.1, BA.2 and BA.3. The subvariant BA.2 has been referred to as “stealth” Omicron because it has genetic mutations that could make it harder to distinguish from the Delta variant using PCR tests as compared to the original version of Omicron. 

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The Omicron variant has been classified as a variant of concern by the WHO and the Centers for Disease Control and Prevention (CDC). The WHO has indicated that since BA.2 is Omicron, it is a variant of concern.

The Omicron variant spreads more easily than the original SARS-CoV-2 strain of the virus that causes COVID-19, and previous variants, including Delta. According to Danish scientists, the Omicron subvariant BA.2, is 1.5 times more transmissible than the original Omicron strain. While there is currently no evidence that the BA.2 lineage is more severe than the BA.1 lineage, experts have warned that BA.2 could extend the current wave of COVID-19 infections in the U.S.

In the Feb. 2, 2022, episode of the COVID-19 Video Update, AMA Director of Science, Medicine and Public Health Andrea Garcia, JD, MPH, said that cases of BA.2 have increased in Denmark, India and in the U.K. and it could drag out the Omicron surge in much of the world.

“In the U.S., BA.2 is about 8% of our cases right now,” Garcia said. “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, which really could translate into that slowing down of the trend we're seeing with cases declining.” 

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Importance of vaccinations & boosters

Peter Hotez, MD, PhD, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Texas Children’s Hospital Center for Vaccine Development in Houston, emphasized the importance of being up to date with COVID-19 vaccinations, including the booster, as a tool to fight any variant. In the Dec. 6, 2021, episode of the COVID-19 Video Update, Dr. Hotez said the booster will “give you the 30- to 40-fold bump in virus-neutralizing antibodies and prolong your immune response."

In a joint statement released in December 2021, the AMA, American Hospital Association, and American Nurses Association, urged the public to get vaccinated and get their booster shots as a way to fight COVID-19 variants. “Science has shown that receiving a booster shot decreases your chance of contracting COVID-19, getting severely sick, ending up in the hospital or dying,” the statement said.

To help protect themselves and others against COVID-19 and its variants, the CDC recommends that the public:

  • Get a COVID-19 vaccine and/or booster.
  • Wear a mask.
  • Stay 6 feet apart from others.
  • Avoid crowds and poorly ventilated indoor spaces.
  • Test to prevent spread to others.
  • Wash hands often with soap and water. Use hand sanitizer if soap and water not available.

The AMA has developed frequently-asked-questions documents on COVID-19 vaccination covering safety, allocation and distribution, administration and more. There are two FAQs, one designed to answer patients’ questions (PDF), and another to address physicians’ COVID-19 vaccine questions (PDF).

The AMA’s COVID-19 resource center has evidence-based news, guidance, videos, podcasts, research highlights and more on the pandemic. Read about the latest on COVID-19 vaccines.

Other key COVID-19 resources include:

Reviewed by: Andrea Garcia, JD, MPH, director of science, medicine & public health, AMA

Reviewed on: Feb. 8, 2022