New Bivalent Omicron COVID-19 Boosters: Effectiveness, Safety, and Other Important Information

An MSK employee (seated) receives a COVID-19 vaccination.

New bivalent booster shots are administered in the exact same way as previous COVID-19 vaccines.

You may have read recently about new booster shots to protect against COVID-19. They have been updated to provide better protection against Omicron subvariants BA.4/5, which are currently the dominant strain in the U.S. These shots were granted Emergency Use Authorization by the U.S. Food and Drug Administration (FDA) on August 31, 2022.

At Memorial Sloan Kettering Cancer Center (MSK), we recommend our patients strongly consider getting the updated booster shot as soon as they are eligible, in order to have the best possible protection from the Omicron subvariants of COVID-19.

Mini Kamboj

Mini Kamboj

Mini Kamboj, Chief Medical Epidemiologist at MSK, has answers to common questions about the shots.

What does it mean that these boosters are bivalent? How are they different?

The term “bivalent” means that they target two strains of COVID-19: the original strain that first appeared in the U.S. in early 2020 and the Omicron subvariants BA.4 and BA.5 that emerged more recently in the summer of 2022. The news media has also referred to these updated boosters as “Omicron-specific.”

These bivalent boosters are made by Pfizer-BioNTech and Moderna using the same technology as the monovalent vaccines that have been given to more than 200 million people in the U.S. They are mRNA vaccines and they work in the exact same way as the original vaccines, but they have been updated slightly for added protection against Omicron BA.4/5.

Since the COVID-19 virus continues to change, it is important that vaccines keep pace. This is not a new approach. Each year, there are new dominant strains of the flu. Scientists create a seasonal flu vaccine that target these strains. The FDA has been planning the same for COVID-19 vaccines and has now taken an important first step: Scientists will regularly produce an updated vaccine so people have the best protection against strains that are spreading or are predicted to spread.

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How effective are the bivalent Omicron boosters?

It’s widely believed in the science and medical communities that these bivalent boosters will work better in preventing Omicron BA.4/5 infections, while keeping the strong protection against severe disease from all COVID-19 strains. Omicron subvariants are predicted to continue to circulate in coming months, and improving protection against this variant is of vital importance.

To evaluate the overall effectiveness of bivalent booster vaccines, a clinical study used a bivalent COVID-19 vaccine that targeted both the original strain of COVID-19 as well as a different Omicron subvariant called BA.1. The data from that study were evaluated by the FDA and led to the Emergency Use Authorization for the new bivalent booster.

In the study, researchers found that people who received the BA.1 bivalent booster had a better immune response against COVID-19 Omicron subvariant BA.1 compared with those who received the original (monovalent) booster. The Moderna part of the study evaluated 600 adults age 18 years and older, while the Pfizer-BioNTech part of the study looked at 600 people age 55 and older. Findings from the two studies were similar.

The FDA thinks that the best course of action now is to authorize this new bivalent booster that targets BA.4/5 instead of BA.1. By replacing the BA.1 component of the booster shot with a BA.4/5 component, we are trying to avoid another potential wave of infections this fall and winter. An independent advisory committee to the CDC endorsed this FDA recommendation on September 2.

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Are the bivalent Omicron boosters safe? How do we know?

These vaccines work in the same way as the original COVID-19 vaccines and booster shots, and they are made using the same process. Because of that, there is no reason to think they will be any less safe. In addition, clinical studies on bivalent boosters so far show that people experience the same side effects as the monovalent vaccines.

To date, more than 610 million doses of COVID-19 vaccine have been given in the U.S. Serious side effects are treatable and have been very rare.

It’s important to note that the FDA, the Centers for Disease Control and Prevention (CDC), and companies that make the vaccines have been rigorously monitoring safety data for primary vaccines and booster shots. That crucial work will continue with these new bivalent boosters.

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Am I eligible to get a bivalent Omicron booster?

There are some important eligibility rules for these new bivalent booster shots:

  • Complete your primary series. To get this new bivalent booster shot, you need to have completed your primary series of COVID-19 vaccination. (The CDC’s website has information about how many doses you need to complete your primary series.)
  • Age matters. The Pfizer-BioNTech bivalent booster is authorized for people ages 5 and older. The Moderna bivalent booster is authorized for people ages 6 and older.
  • Boosted before September 1? You are still eligible. If you received 1 or more booster shot(s), you are still eligible for a bivalent booster. If you didn’t receive any booster shots yet, you’re also eligible.
  • Wait 2 months. Whenever your most recent COVID-19 shot was, you must wait 2 months before getting a bivalent shot.
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What about children under age 5?

For children ages 4 and younger, the FDA has not yet authorized any booster shot.

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What about people who have cancer or have had cancer? Can they get the bivalent booster?

Yes. At MSK, we strongly encourage all of our patients to get vaccinated and boosted.

People who have cancer now or who have had cancer may have a weakened immune system because of the disease or its treatment. Because of this, they are particularly susceptible to severe COVID-19. These new bivalent boosters provide another layer of protection beyond the primary vaccine shots and booster shots that you may have received.

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What about people who are pregnant, expecting to become pregnant, or are breastfeeding? Can they get a bivalent booster shot? Should they?

Yes. People who are pregnant, expecting to become pregnant, or are breastfeeding are eligible to get a new bivalent booster shot. It is well understood that primary COVID-19 vaccines and regular (monovalent) booster shots are safe and effective for this group. There is no reason to believe that this will be different for bivalent boosters.

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Can I still get the regular (monovalent) COVID-19 booster shot? What if I just completed my primary vaccine series?

No. With the FDA authorization of these bivalent boosters, they also removed authorization for monovalent boosters.

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If the bivalent booster provides better protection, can I get it as my primary shot?

No. The bivalent boosters have not been developed for that purpose yet. They are currently designed to be used as booster shots, meaning they have only been studied in previously vaccinated people. In coming months, the bivalent vaccine may be recommended as the COVID-19 vaccine primary series once ongoing studies are completed.

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I was infected with COVID-19 recently. Should I get the new bivalent booster? When?

Yes, it’s recommended that people who have been infected with COVID-19 should still get the bivalent booster.

We know from past research that primary vaccination and booster doses after infection increase protection against future infection and severe disease. This applies to bivalent booster shots too.

People who were recently infected may choose to wait 3 months to receive their booster shot.

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Can I get the bivalent booster at the same time as my flu vaccine?

Yes. All COVID-19 vaccines (including boosters) are safe and effective when given with other vaccines. There is no specific time interval that is recommended between routine vaccinations and the COVID-19 vaccine. The most important thing is that you take both vaccines. Whether it is on the same day or different days, that is your choice.

If vaccinated on the same day, it is recommended that the shots are given in different arms.

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Should I get the same brand of bivalent booster as my other shots? Or can I mix and match between brands?

It is acceptable to mix and match if the booster is approved for your age group. You can switch brands again or stick with what you’ve received in the past.

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I am eligible for the bivalent Omicron booster. When should I get it?

You should take the bivalent booster as soon as you can. The variants targeted by the updated bivalent booster (Omicron BA.4/5) are expected to continue to circulate throughout the U.S.

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Can I get my bivalent booster shot at MSK? How do I schedule an appointment?

Adult patients can schedule their bivalent booster shot at MSK using this link »

For pediatric patients, you will need to call your child’s primary care doctor at MSK. A parent or guardian must be on-site to consent to their child getting the vaccine. They cannot give consent over the phone or electronically.

However, there is no need to wait to be vaccinated at MSK. We encourage patients to use the following websites to find a location with vaccine availability:


October 12, 2022

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