How worried should we be about the new ‘stealth’ Omicron? Our expert weighs in

A new subvariant of Omicron is spreading rapidly in some parts of the world. This spinoff from the original Omicron variant, called BA.2, has been found in at least 49 countries, including the United States. In some countries, like Denmark, BA.2 has already surpassed the original Omicron (BA.1) as the dominant variant.

Because it doesn’t cause a certain signature on lab tests called an s-gene target failure, it can look like other coronavirus variants on a first screen. That has some calling it “the stealth variant.”

How worried should we about this “stealth” Omicron? Are vaccinated people still protected? What about those who recently had Covid-19—could they be reinfected? And can tests pick up this subvariant?

A healthcare worker places a test swab into solution for a PCR Covid-19 test at a testing site in Hawthorne, California on January 18, 2022.

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For answers to these and other questions, I spoke with CNN Medical Analyst Dr. Leana Wen. Wen is an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health. She is also the author of “Lifelines: A Doctor’s Journey in the Fight for Public Health.”

CNN: Should we be worried about this new Omicron subvariant?

Dr. Leana Wen: We should be cautious and monitor new information as it comes out, but we shouldn’t worry.

Here’s what we know about BA.2. Given how quickly it has spread and even displaced the very contagious original Omicron variant, known as BA.1, in some places, this new subvariant appears to have an even higher rate of growth. There’s no evidence that it causes more severe disease than the original Omicron, which has been associated with milder illness than previous variants like Delta.

Preliminary studies from the United Kingdom also show that people vaccinated and boosted are as well-protected against BA.2 as BA.1. That’s very important, because it means that those vaccinated and boosted are unlikely to become severely ill if infected with this new version of Omicron.

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CNN: If you’re diagnosed with Covid-19, how would you know if you have the original Omicron variant versus this one?

Wen: Most people do not find out what variant they are infected with, because that takes special technology called sequencing that takes place in certain labs. Right now, the original Omicron BA.1 still accounts for over 99% of new infections in the US, so if you are diagnosed with Covid-19, chances are, that’s what you have.

A healthcare worker places solution droplets into a rapid antigen Covid-19 test at a Reliant Health Services testing site in Hawthorne, California, on January 18.

CNN: If someone recently had Omicron, could they get reinfected with the new variant?

Wen: It’s unlikely. Recent infection, especially in combination with prior vaccination, protects against reinfection. We don’t know how long that immune protection will last. Given how similar BA.1 and BA.2 are to each other, it stands to reason that someone who just had Covid-19, and therefore most likely had BA.1, is not going to contract BA.2 in the near future.

A man receives a COVID-19 booster shot at a clinic in Mountain Home, Arkansas. Dsc 0200

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CNN: Will the new Omicron-specific booster work against BA.2?

Wen: Pfizer and Moderna have announced that they are both testing vaccines against Omicron. Since both BA.1 and BA.2 are subvariants under Omicron, it’s expected that the vaccine would probably be effective against both.

However, we will not know until the clinical trials are complete just how effective the new Omicron-specific booster is, compared to the vaccine and booster that we have already been using. No one should wait for an Omicron-specific booster if they are already eligible to be boosted. If you are five months out from two doses of Pfizer or Moderna, or two months out from the one-dose Johnson & Johnson vaccine, you should get a booster now.

CNN: What could happen if BA.2 becomes dominant in the US?

Wen: This is certainly a possibility, as it has occurred in other countries. A more transmissible variant means that it displaces previous variants.

The best-case scenario is that we have enough people protected here in the US due to vaccination and recent infection that BA.2 does not cause a substantial rise in cases. We could continue on the track to experiencing a lull in case numbers over the spring and summer. Another scenario is that BA.2 blunts the sharp drop in cases that we are seeing, and we end up having a more prolonged fourth wave than we would have with BA.1 alone.

In either situation, the key is to keep monitoring whether vaccination and boosters continue to protect against severe illness from BA.1 and BA.2. If so, that means vaccines are successful—that’s what vaccines were designed to do, to keep us out of the hospital and to prevent severe illness and death.

CNN: Does “stealth” mean that the new subvariant isn’t picked up on tests?

Wen: No, there’s no evidence to suggest that BA.2 isn’t detectable with laboratory PCR or at-home antigen tests.

A child receives a dose of the Pfizer-BioNTech Covid-19 vaccine at a vaccination clinic at an elementary school in San Jose, California, on Nov. 4, 2021.

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CNN: What’s your advice for protecting myself and my family from this subvariant?

Wen: There are many people who want to continue taking precautions to keep from getting infected with Covid-19: those who are immunocompromised, for example, or others who are medically frail and therefore still vulnerable to severe outcomes despite being vaccinated. There are families with young children under 5 who are not yet eligible for the vaccine, although it looks like that could be coming.

Another contagious virus means that people who want to avoid getting Covid-19 have to continue taking precautions. The most important is indoor masking, and quality of mask really matters. The best mask is a well-fitting, comfortable one that you can consistently wear and is a certified N95, KN95 or KF94.

Wear these masks anytime you are indoors around people of unknown vaccination status. While coronavirus infection numbers are high in your community, you may want to take additional precautions—for example, asking everyone outside your household to get a rapid test prior to gathering with you indoors.

CNN: Will this be the last variant we see?

Wen: Almost certainly not. New variants are popping up all the time, because that’s what viruses do: They mutate when they replicate. Whether a new variant causes global concern depends on if it’s more contagious, more virulent or if it can override prior immunity. This is why real-time surveillance is so important, and it’s also why vaccination is key. The more population immunity we have, the less viruses will spread and mutate, and the quicker we can all emerge from this pandemic.