All kids over age 6 months who are eligible for a Covid booster may now get an updated vaccine formulation, known as a bivalent booster.

The Food and Drug Administration (FDA) has newly authorized Pfizer’s bivalent booster for kids 6 months and up. For those who have received a full course of Pfizer-BioNTech’s three-shot monovalent series and are eligible for a booster dose (two months after the third shot), they may now receive Pfizer’s bivalent booster. The Centers for Disease Control and Prevention (CDC) will still need to sign off on the authorization, at which point shots will be made available to this new group.

With the bivalent booster, both Pfizer-BioNTech and Moderna have updated their Covid vaccines to add an Omicron BA.4/BA.5 spike protein component to the current vaccine composition, which can help the immune system better recognize the virus even though it has mutated.

Kids under 5 who received a bivalent dose as the third dose of their primary Pfizer series are not eligible for a new booster, as their previous vaccination is expected to continue to provide protection against Omicron strains.

Previously, bivalent boosters were only available for kids ages 6 months to 4 years who had received the Moderna 2-shot series, or for everyone over age 5. But the expanded access means even more kids across the country will now be eligible to receive an updated shot that better protects them against the Omicron variants, though uptake of the bivalent boosters in general remains low—and uptake in the under-5 age group is also low. Just 4% of children under 2 years and 6% of children ages 2 to 4 years have completed a primary series with any vaccine, according to CDC data.

Bivalent boosters are intended to help ward off a new surge in Covid case numbers. Per AAP data, almost 15.5 million Covid cases among children have been reported as of March 9.

Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said the FDA authorization will give eligible families “an opportunity to update their children’s protection.”

“Currently available data show that vaccination remains the best defense against severe disease, hospitalization and death caused by COVID-19 across all age groups, and we encourage all eligible individuals to make sure that their vaccinations are up to date with a bivalent COVID-19 vaccine,” Dr. Marks said in a press release.

The current vaccine formulations are still highly effective at preventing severe disease from Covid, but are significantly less effective at protecting against symptomatic illness, given that the virus has mutated so much since vaccines were first issued. The hope is that a single-dose booster will offer more expanded protection against the latest Omicron subvariants.

But does your child need a Covid booster, and how can you know if they are eligible? We’re answering your questions here.

Related: What parents need to know about BA.5, the Omicron subvariant

What is a bivalent booster?

A bivalent booster is a vaccine formulation that helps the immune system mount an immune response against two different antigens, like two different strains of the same virus. Bivalent Covid vaccines offer protection against both the original virus SARS-CoV-2 and the Omicron subvariant.

Just like the original vaccines, the boosters have a high safety profile, and the boosters are manufactured using the same process as the original (monovalent) vaccines. The most common side effects include irritability, drowsiness, pain at injection site, fatigue or fever.

“The updated COVID-19 boosters are formulated to better protect against the most recently circulating COVID-19 variant,” CDC Director Rochelle P. Walensky, MD, MPH, said in a press release. “They can help restore protection that has waned since previous vaccination and were designed to provide broader protection against newer variants. This recommendation followed a comprehensive scientific evaluation and robust scientific discussion.” 

How do I know if my child will be eligible for a booster? 

You’ll want to check your child’s Covid vaccination record card to confirm the dates and types of vaccines your child received.

  • If your child over 6 months has received a primary Moderna vaccine series and/or a booster, the updated guidelines state that they will be eligible for a single-dose bivalent booster once it has been at least 2 months since the last dose of their primary series or their last booster.
  • If the CDC recommends the Pfizer booster for those who received the monovalent Pfizer primary series, they’ll soon be eligible, too.
  • If your child received a bivalent booster as the third shot in their primary Pfizer series, they won’t be eligible for another bivalent booster.

Related: Having young kids might protect you from severe Covid, study shows 

What if my child recently had Covid? 

Most adults and kids are now walking around with some level of immunity to the coronavirus, whether that’s from vaccines or infection. But how well that immunity protects you seems to be quickly waning. That means that yes, you or your child can get Covid more than once, even if you’ve been recently infected—and even if you’ve had a previous version of Omicron (which is likely if you’ve been infected since January 2022). 

Unfortunately, we’re seeing many instances of repeat infections around the world, which suggests that the former thinking that prior infection gave you a natural immunity for up to three months may no longer hold when it comes to BA.4/BA.5. 

Experts stress that there’s an abundance of evidence that boosters will protect against severe disease. Plus, there’s the consideration that the more people who are fully vaccinated, the less the vaccine is able to spread and eventually mutate, experts say.

Related: Got questions about the Covid vaccine for kids under 5? We’ve got answers

A version of this story was originally published on Aug. 19, 2022. It has been updated.

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