What We Know About Omicron Subvariants BA.4 and BA.5

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Microbiologist Esther Babady in her lab

Esther Babady is Director of MSK’s Clinical Microbiology Service.

There are many questions about the variants of COVID-19, and scientists are learning more every day. The most widely circulating variants in the U.S. right now are the Omicron subvariants BA.4 and BA.5.

Esther Babady, Chief of MSK’s Clinical Microbiology Service, is a nationally recognized leader in understanding variants and testing for COVID-19.

Here, Dr. Babady answers questions you may have about variants and how to protect yourself.

This information is about the Omicron subvariants BA.4 and BA.5.

Read about bivalent booster shots, which target Omicron subvariants BA.4 and BA.5 »

What are Omicron subvariants? What does it mean when a new subvariant emerges?

When scientists find variants and subvariants, it means the virus is changing as it persists within a person or moves from person to person throughout the population.

There are several members of the Omicron variant group. They all have different mutations in their genome, which means they have different characteristics.

The surge of COVID-19 cases in January and February 2022 was primarily driven by Omicron BA.1. Then, another surge in March, April, and May was driven by BA.2. Omicron subvariant BA.3 did not spread widely. Today, most cases of COVID-19 are caused by the BA.4 and BA.5 subvariants.

Variants and subvariants are expected and something that we plan for. As a science and healthcare community, we are focused on BA.4 and BA.5 but we’re also looking ahead to what could come next.

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What can I do to protect myself from Omicron BA.4, BA.5, and other COVID-19 variants and subvariants?

There are several things you can do to protect yourself and your loved ones. We know that all of these actions slow the spread of COVID-19.

  • Get vaccinated and get the bivalent booster shot: Getting your initial vaccination and following up with a bivalent booster shot can protect against severe illness and can stop the virus from spreading easily. New bivalent booster shots were granted FDA Emergency Use Authorization in late August 2022. These are called “bivalent” because they target two strains of COVID-19: the original strain that emerged in the U.S. in early 2020, and the Omicron subvariants BA.4 and BA.5. Read more about new bivalent booster shots »
  • Test: You should take a test if you aren’t feeling well, if you were exposed to someone with COVID-19, or if you are going to see someone who is high risk for COVID-19. Keep reading this story or click here to learn more about testing for BA.4 and BA.5 »
  • Wear a mask: Wear a mask indoors and outdoors if you are immunocompromised, not fully vaccinated, physical distancing is not possible, or if COVID-19 rates are high where you live. Read more about when to wear a mask and which type of mask is best »
  • Stay home when you are sick
  • Wash your hands frequently
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Are BA.4 and BA.5 more contagious than other variants? Do these subvariants cause more severe disease?

These subvariants spread easily across the U.S. As cases rise, generally, hospitalizations and deaths also go up. However, there is no definitive proof that BA.4 or BA.5 subvariants cause more severe disease in people.

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Should I be worried about BA.4 and BA.5?

These subvariants should be taken seriously. The risk of getting infected with COVID-19 is as high as it has ever been.

The Omicron variant group is labeled by the Centers for Disease Control and Prevention (CDC) as a “variant of concern.” The CDC says a variant of concern could have several possible attributes, including any or all of the following:

  • increased transmissibility
  • increased disease severity
  • decreased vaccine protection

Since BA.4 and BA.5 are part the Omicron variant group, they are also considered variants of concern.

Read more about how the CDC defines a variant of concern »

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Can the BA.4 and BA.5 subvariants be detected by current at-home diagnostic tests?

Yes. Current at-home diagnostic tests detected BA.4 and BA.5. Anecdotally, there have been cases of people who felt sick but still tested negative several times with at-home tests. This suggests a potential decrease in the sensitivity of some at-home tests.

However, that doesn’t mean you shouldn’t test. If you have symptoms or were exposed to someone with COVID-19, you should get a PCR test or consider testing twice per day with an at-home test.

If you are going to see someone who is at high risk for severe COVID-19, you should take an at-home test — even if you are feeling fine.

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If I already had COVID-19 recently, can I get sick again with the Omicron subvariant BA.4 or BA.5?

It’s possible. There have been cases of people who were infected just a few weeks ago and already have COVID-19 again. How frequently this happens is still under investigation. Infection with another COVID-19 subvariant may or may not provide natural immunity against BA.4 or BA.5. We need more data to fully understand this.


September 14, 2022


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