Which COVID-19 Vaccine Should Your Kid Under 5 Get?

Some of the U.S.’s youngest children are getting COVID-19 vaccinations. Now, parents have to decide if they want Moderna or BioNTech.

Both of the mRNA shots—which are now authorized for kids ages 6 months and up—are effective at preventing severe illness, and they both help prevent symptomatic infections. Even for children who are already free from COVID-19, they offer crucial protection. The vaccines “provide protection against a broader variety of variants than [a previous] infection, which generally provides protection mostly against the variant that you had,” says Dr. Alissa Kahn, a pediatric hematologist and oncologist in Paterson, N.J. That’s particularly important as the virus evolves to overcome prior immunity. Each time an unvaccinated child is exposed to SARS-CoV-2, “you’re sort of rolling the dice—and most kids will do well, but sometimes they don’t.” Since the start of the pandemic, more than 440 children under 5 in the U.S. have died.

But unlike with the adult shots—where the best shot was the one you could get quickly—there are some key differences between the two under-5 vaccines.

“The science behind how they work is the same,” says Dr. Mona Amin, a pediatrician in Fort Lauderdale, Fla. “The difference is the schedule and the dose.”

Moderna’s vaccine for kids ages 6 months through 5 years is 25 micrograms (mcg)—one-quarter of the dose that adults get. Pfizer’s shot for kids 6 months through 4 years is 3 mcg—one-tenth the adult dose. According to trials data, the Moderna shot has milder side effects than the adult dose.

Different timelines for vaccination are available. Moderna’s vaccine involves two shots four weeks apart, while Pfizer’s requires three shots over 11 weeks. Moderna has one less shot, but Pfizer is more effective and can cause fewer side effect. Pfizer takes several additional weeks to fully inoculate the children.

If parents want kids to be protected as soon as possible—a particular concern with most schools starting in a couple of months—they might want to go with Moderna. That’s what Kahn is choosing for her 4-year old son. The faster Moderna timeline “is really going to allow parents to be able to send their kids to school in the fall fully vaccinated, which is important for a lot of families,” she says.

Moderna is also the “pretty clear” choice for Dr. Alpa P. Shah, a pediatrician in Milwaukee. Shah worries about her 2-year-old daughter’s exposure to elementary-aged children this fall, as she attends school that has preschool for them. “The timeline is much more friendly for the fall with Moderna,” she says. Families who would prefer to have two shots than three due to transportation problems or lack of time at work might find Moderna more attractive.

But if parents are concerned about side effects, and they’re not in a particular hurry, Pfizer might be a better option. Some families may be hesitant to get vaccinated if they have the choice of a lower dose that has a reduced risk of side effects. A third Pfizer shot seems to produce a wider range of antibody responses that likely aid Omicron.

That’s what Amin is choosing for her 2-year-old son. He already had COVID-19 twice, and while that doesn’t offer complete protection against reinfection, it means his existing immune response could be strong even before he gets a third shot.

Amin likes that Pfizer has been administered to many millions of children ages 5 and over, while Moderna was available only for U.S. citizens until June 24, when it was recommended for use by kids. That means there are more real-world data on Pfizer’s side effects among older children, including very rare side effects like myocarditis.

Roby Bhattacharyya is an infectious disease physician at Massachusetts General Hospital. He debated which vaccine to give his son, who’s now four years old. “The data for either one looks great, far above my threshold for where the expected benefits exceed the risks,” he writes in an email. “If only one or the other were available, I’d take either in a heartbeat for my kid.”

He decided that the best thing to do was get a vaccination as soon as possible. “Our kids are starting camp, and I think the cost of waiting another 10 days where they’re hanging out in close quarters with a bunch of kids at a time when there’s still a decent amount of circulating virus is more risk than any difference I see between these two, both of which I see as good options,” Bhattacharyya writes. A few hours later, his son received the first vaccine they could schedule: Pfizer’s.

That’s fairly typical right now; some pediatricians and health systems are only carrying the Pfizer shot, at least at first, because they already have a system set up for giving Pfizer to older kids. Providers had already ordered 2.5 Million Pfizer doses and 1.3 Mio Moderna doses by mid-June. But if you only have access to one type of vaccine, even if it’s not your preference, you shouldn’t feel like you’re getting an inferior vaccine, the experts agreed.

The under-5 vaccines don’t generally have the same availability as those for older ages. These vaccines were usually administered in schools or mass vaccination centers. Most families visit their doctor or general practitioner instead. They can also be seen by pharmacies which, according to law, cannot give COVID-19 vaccinations to children under 3 years old. (If you’re looking to set up an appointment, you can search by vaccine type at

“I would just love to see both vaccines available in all states and distributed in an equitable fashion,” Shah says, “so families can really choose what makes sense to them.”

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