New COVID-19 boosters are coming. Here's what parents need to know about the updated vaccines.

A child wearing a face mask receives a vaccine.
Kids as young as 6 months will be able to receive the updated COVID-19 vaccine. (Getty Images)

The Food and Drug Administration just approved the long-anticipated updated COVID-19 vaccine and booster for Americans. The updated mRNA vaccines are produced by Moderna and Pfizer, and will replace previous versions of the COVID-19 vaccine.

“Vaccination remains critical to public health and continued protection against serious consequences of COVID-19, including hospitalization and death,” Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a statement announcing the approval. “The public can be assured that these updated vaccines have met the agency’s rigorous scientific standards for safety, effectiveness, and manufacturing quality. We very much encourage those who are eligible to consider getting vaccinated.”

That was followed by the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) voting 13 to 1 to recommend the vaccines for Americans aged 6 months and up.

With this, it's understandable for parents to have questions about what the updated vaccines mean for their families. Here, infectious disease doctors tackle some of the biggest questions.

What is the new COVID-19 vaccine?

The new COVID-19 vaccine is actually two vaccines — one available from Moderna and one from Pfizer, similar to previous versions of the vaccine and booster. These vaccines have been updated to include a monovalent (aka single) component that corresponds to the Omicron variant XBB.1.5.

Who is the new COVID-19 vaccine for?

Here's a breakdown of specifics:

  • Kids 5 and older, regardless of previous vaccination, are eligible to receive a single dose of an updated mRNA COVID-19 vaccine at least two months since the last dose of any COVID-19 vaccine.

  • Kids 6 months through 4 years of age who have previously been vaccinated against COVID-19 are eligible to receive one or two doses of an updated mRNA COVID-19 vaccine. The timing and number of doses depends on the previous COVID-19 vaccine received.

  • Unvaccinated kids age 6 months through 4 years are eligible to receive three doses of the updated authorized Pfizer-BioNTech COVID-19 vaccine or two doses of the updated authorized Moderna COVID-19 vaccine.

What happens if my child hasn't had a COVID vaccine before?

If your child is 5 or older, they will just get one dose of the vaccine, per the FDA. Why just one? It's assumed that, by age 5, kids would have either had COVID-19 or been exposed to the virus, infectious-disease expert Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life.

But if your child is 4 or younger, they will need to get three doses of the updated authorized Pfizer-BioNTech vaccine or two doses of the updated authorized Moderna vaccine.

What are the side effects of the new vaccine?

According to the FDA, there should be no new side effects from the updated vaccine. Per the CDC, those can include:

For kids 6 months to 3 years:

  • Pain on the leg or arm where the shot was given

  • Swollen lymph nodes

  • Irritability or crying

  • Sleepiness

  • Loss of appetite

For children 4 to 17 years:

  • Pain, swelling and redness on the arm where the shot was given

  • Tiredness

  • Headache

  • Muscle or joint pain

  • Chills

  • Swollen lymph nodes

What happens to the old COVID-19 vaccine?

The new vaccine will replace the old one, Adalja says. "The new XBB monovalent COVID vaccine will be the only version of the vaccine available," he says. "The prior versions of the vaccine target strains of the virus that no longer circulate."

The old vaccine will simply be "withdrawn and resupplied with this new vaccine," Dr. William Schaffner, an infectious-disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Life.

Why is the vaccine "approved" for some age groups and "authorized" for others?

The FDA made a point to say that the updated mRNA vaccines are each approved for kids 12 and older and are authorized under emergency use for individuals 6 months through 11 years of age. "The youngest age group is still under EUA [emergency use authorization] because of the amount of data provided to the FDA regarding the vaccine in this age group," Adalja says. "A full FDA approval requires more data than an EUA."

Who should get the new COVID vaccine?

The updated vaccine is recommended as more of a priority for children who are immunocompromised or have medical complications, Dr. Ian Michelow, division head of pediatric infectious diseases and immunology at Connecticut Children's Specialty Group, tells Yahoo Life. "Children overall are generally at low risk of complications of COVID," he says. "But I still suspect that there will be a recommendation to get the vaccine, because we know they're effective at preventing severe complications. Even though we know the risk is low, it's not zero."

Ultimately, Michelow says, "it will be up to families to decide if this is something they want to do."

This article was originally published on Sept. 11, 2023 and has been updated.