Last week, the US Food and Drug Administration approved the bivalent Covid-19 booster for children ages 6 months to 5 years old. The U.S. Centers for Disease Control and Prevention has since recommended the booster, and now anyone 6 months and older can receive the updated coronavirus vaccine, except children who received three doses produced by Pfizer/BioNTech.
Which young children are now eligible for the booster? What if kids didn’t start or complete the full series – will they get the updated booster or the original monovalent vaccine now? Can parents and guardians choose between the updated booster and the original recording? What are possible side effects? What if children already had Covid-19? And which families should consider the updated booster now, and who can wait?
To help us answer these questions, I spoke with CNN Medical Analyst Dr. Leana Wen, an emergency physician, public health expert, and professor of health policy and management at the George Washington University Milken Institute School of Public Health. She is also the author of “Lifelines: A Doctor’s Journey in the Fight for Public Health” and a mother of two young children, ages 2 and 5.
CNN: Let’s start with what just changed in the recommendations: Which young children who received the Pfizer or Moderna vaccine are now eligible for the booster?
Dr Leana Wen: Two vaccines have been approved for young children: Moderna and Pfizer. For the youngest age group, the Moderna vaccine was designed as a two-dose primary vaccine, while the Pfizer version was designed as a three-dose primary vaccine. That means young children are considered to have completed their primary series if they have completed two doses of the Moderna vaccine or if they have completed three doses of Pfizer.
As a reminder, a bivalent booster is now available for older children and adults. This combines the original (also called monovalent) vaccine with a vaccine that specifically targets the BA.4 and BA.5 Omicron subvariants. Since Omicron subvariants account for virtually all new infections, the hope is that the bivalent booster will provide better, more targeted protection.
What federal health officials have now said is that children 6 months through 5 years old who received both doses of the original Moderna vaccine can receive the updated bivalent vaccine — if it’s been at least two months since they received the primary vaccine series completed.
For children who received the Pfizer vaccine, the guidance is slightly different because the primary series already includes three doses. Federal health officials have said children ages 6 months through 4 years old who have not yet completed their three vaccine doses can receive the third dose as the bivalent vaccine. Let’s say a child started this series and had one or two doses of the original Pfizer vaccine. The third dose can now be the upgraded booster.
CNN: What if kids didn’t start or complete the full series – will they get the updated booster or the original monovalent vaccine now?
Wen: The answer is different for Moderna vs. Pfizer. For Moderna, the primary series is two doses, so a child must complete the first two shots with the original formulation. The booster – the third dose – is the bivalent vaccine. For Pfizer, the primary series is three doses. The first two doses should still be the original formulation, but the third injection is now the bivalent vaccine.
CNN: What about young children who have completed three doses of the Pfizer vaccine – are they eligible for a fourth dose?
Wen: No. The FDA explicitly says that children 6 months through 4 years old who have completed their three-dose primary series of the original Pfizer vaccine are not eligible for a fourth injection of the bivalent booster. That’s because the primary series of three vaccine doses is still expected to provide strong protection against serious disease for Omicron. This recommendation will be re-evaluated as new data become available.
CNN: Can parents and caregivers who have not completed the Moderna primary series choose the bivalent vaccine as their second dose?
Wen: No. The FDA authorization for the adult primary series for Moderna – the two doses – is for the original monovalent vaccine. Similarly, there is no choice of which vaccine formulation is administered as a booster for Pfizer in adults. Only the bivalent booster is available as a third injection, not the original monovalent, which is still given as doses one and two. This mirrors the authorization given for adults – the primary series is the monovalent vaccine, with the only booster for Pfizer and Moderna for adults being the updated booster.
CNN: What are possible side effects of the updated booster?
Wen: Children receiving the updated booster are expected to experience similar types of side effects to the original vaccines. These side effects are usually mild and short-lived and usually disappear within the first 24 hours after vaccination. Side effects may include pain and swelling at the injection site, tiredness, moodiness, drowsiness, headache, muscle aches, and sometimes fever. Many children experience no side effects. The risk of serious side effects, such as myocarditis (an inflammation of the heart muscle), is expected to be extremely rare in this younger age group.
CNN: What if kids already had Covid-19?
Wen: People who have had Covid-19 can wait three months until they have recovered from the coronavirus to get another vaccine dose, according to the CDC. They probably have very good protection against infection during this time.
Many studies have shown that hybrid immunity – recovery from Covid-19 in combination with vaccination – offers very strong protection, arguably even more than vaccination and boosters alone. In my opinion, I think it can be assumed that if a young child were given the primary series and already had Covid, they could wait to get another booster dose. This is especially true if they have had Covid recently, within the past year. To my knowledge, there is no research showing additional benefits of boosters for young children who have recently had a Covid-19 infection and who have received their primary vaccinations.
CNN: Which families should consider the updated booster now and who should wait?
Wen: First, I think it’s important to point out that the uptake of the primary series of the Covid-19 vaccines among young children is very low. According to the CDC, less than 5% of children ages 5 and younger are fully vaccinated. That means we’re talking about a very small group of kids newly eligible for the updated boosters.
There is one group that I would definitely recommend buying the updated booster. That’s the group of kids who received their first one or two doses of the Pfizer vaccine. These kids must complete their primary series. The third dose of that series is now the renewed bivalent booster. There is no reason for families of these children to wait; they should complete the primary series, and it’s a bonus that the third dose is updated to target Omicron.
For children who received the two doses of the Moderna vaccine, I think the decision making is different and will depend on the individual circumstances of the family. Some families are very concerned about the Covid-19 infection. Perhaps their child has underlying medical conditions, or they live with someone who is older, immunocompromised, or otherwise very vulnerable to severe effects from Covid-19. Perhaps the family will be welcoming a newborn soon and that baby is particularly vulnerable to a coronavirus infection. I think it’s fair to conclude that as Covid-19 cases are on the rise, now is the time to get their young child the updated booster.
I also think it is reasonable to wait. My kids (ages 2 and 5) got the Moderna vaccines in the summer. They’re eligible for a boost, but I’m holding off on it because the protection they have against serious illness remains strong. The booster provides additional protection against symptomatic infection, but that effect is likely to be short-lived, according to a June study.
To be clear, I think it is crucial for older adults and vulnerable individuals to receive the updated booster. I also think it’s generally a good thing that people can choose the booster if they want to because there are compelling individual reasons for different households.
Parents and carers who have questions should consult their pediatrician to decide the best course of action for their family’s specific circumstances. Finally, families whose children have not yet received Covid-19 vaccines should consider starting, especially if their children are not known to have had Covid-19.