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Your Guide to the Bivalent COVID-19 Booster Vaccine

Contributor: Erica S. Shenoy, MD, PhD
7 minute read
Patient receives COVID booster shot

The Centers for Disease Control and Prevention (CDC) have approved and recommended updated bivalent COVID-19 vaccines from Pfizer and Moderna. These vaccine boosters protect against the original strain of COVID-19 and the Omicron variant, which is currently spreading in the United States.

Erica S. Shenoy, MD, PhD, medical director of infection control for Mass General Brigham and an infectious diseases physician at Massachusetts General Hospital, answers patients’ common questions about the bivalent COVID-19 booster. 

Q: How is the COVID-19 bivalent booster different from past booster shots?

Shenoy: Bivalent vaccines were developed to protect against two different viruses or two strains of the same virus. In this case, the updated COVID-19 boosters target the original COVID-19 strain and two Omicron variants (Omicron BA.4 and BA.5).

Q: Who can receive an updated booster?

Shenoy: If you’re age 5 and older, you can receive the new bivalent booster if:

  • You’ve received all vaccines in your primary vaccination series, and
  • At least 2 months have passed since you received your last COVID-19 vaccine dose (either your final primary series dose or an original monovalent booster dose)

The Pfizer bivalent COVID booster is approved for age 5 and above. The Moderna booster is approved for age 6 and above.

On December 9, 2022, the bivalent COVID-19 vaccines were also approved for infants and children ages 6 months through 4 years old by the U.S. Food and Drug Administration (FDA) and the CDC. It should be used as a third dose in children ages 6 months to 4 years.

Right now, COVID-19 and flu are circulating in our communities. Make sure you are well protected from serious disease with available vaccines.

Erica S. Shenoy, MD, PhD
Infectious Diseases Doctor
Mass General Brigham

Q: Which children ages 6 months through 4 years can get a bivalent COVID-19 vaccine?

Shenoy: Most children who have:

  • Received the 2-dose Moderna primary series are eligible for a bivalent Moderna vaccine booster 2 months after they completed their primary vaccine series.
  • Received 2 doses of the 3-dose Pfizer primary series are eligible for a bivalent Pfizer vaccine 2 months after their second vaccine. This is their third dose.
  • Received and completed the 3-dose Pfizer primary series are not eligible for the bivalent vaccine at this time. 
  • Not been vaccinated can start either the Moderna or Pfizer series. They will get the bivalent COVID-19 vaccine as a third dose. 

For children who are immunocompromised, the vaccine schedule may differ.

Q: What if my child has not received the primary COVID-19 vaccine series?

Shenoy: Your child should still get their primary vaccine series. The original vaccines are approved by the CDC for the first 2 doses of the primary vaccine series. The primary vaccine series still protects your child from the virus. The bivalent vaccine provides your child with added protection from the virus.

Q: When should I get my bivalent COVID-19 booster? Can I get my annual flu vaccine at the same time?

Shenoy: There’s no time like the present. I’d recommend getting your COVID-19 booster when you’re eligible. You can get both your COVID-19 booster and your flu vaccine at the same time. If you haven’t yet received your flu vaccine, you should get it as soon as possible.

Let’s start with the COVID-19 booster: Right now, COVID-19 and flu are circulating in our communities. Make sure you are well protected from serious disease with available vaccines.

We’ve had an early flu season this year, and while flu activity is decreasing, you can still take advantage of the flu vaccine’s protection.

If you decide to get both at the same time, that can be a time-saver and very convenient. There’s no reason not to get both the same day. It’s safe to do so and can save you an extra visit to the pharmacy or your doctor’s office.

Q: Where can I get my bivalent COVID-19 booster vaccine?

Shenoy: To find a bivalent COVID booster location near you, visit one of the following sites:

You can also find an updated COVID booster location by texting your zip code to 438829 or calling 1-800-232-0233.

Mass General Brigham offers the updated booster vaccine at many primary care offices and some specialty offices during regularly scheduled office visits. Mass General Brigham will also continue to distribute vaccines from our mobile community vans. Check the schedule to see if the vans will be near you.

Q: What are common side effects from the COVID-19 bivalent booster?

Shenoy: Reported side effects seem to be the same as the original vaccine. Side effects are usually mild and go away on their own. The CDC has some good guidance on simple things you can do to reduce the severity.

These include:

  • Drinking plenty of fluids
  • Getting plenty of rest
  • Moving the arm in which you receive the shot to reduce pain or swelling

Q: How long do you expect bivalent booster protection to last?

Shenoy: That’s a great question. We know that immunity (your body’s ability to resist the virus) wanes over time. But the strength of protection also depends on how the virus evolves and whether future variants, such as the newest one (XBB.1.5), escape the vaccine-induced immunity or not. I think we will start to see some emerging data on this as it collects over time.

Q: Can I “mix and match” vaccines (for example, Pfizer with Moderna)? Or should my booster be the same as my first vaccine?

Shenoy: The CDC doesn't recommend mixing vaccine products for your primary series. However, you can get a different product for the updated booster, except for 5-year-old children, for whom the Pfizer updated booster is the only recommended booster. For people ages 6 and older, they can receive either Moderna or Pfizer as their updated booster. That can be different from what they received previously for their primary series or any doses of the monovalent booster.

Last updated 1/17/2023

Headshot of Erica S. Shenoy, MD, PhD


Infectious Diseases Doctor