How COVID Vaccine Dosage Is Different For Young Kids

What parents need to know about the Pfizer vaccine — and why kids age 5-11 will get a much smaller dose.
Children ages 5–11 could be eligible for COVID vaccines in the coming weeks. Here's what parents need to know about the dosage.
Jasmin Merdan via Getty Images
Children ages 5–11 could be eligible for COVID vaccines in the coming weeks. Here's what parents need to know about the dosage.

For months now, many parents have anxiously awaited the day when children under 12 will be eligible for COVID-19 vaccination, wondering: What’s the hold-up?

Well, the “hold-up” has basically been that researchers have been looking closely at dosing, testing smaller amounts in younger children to make sure they’re both safe and effective.

As Dr. Janet Englund, a professor of pediatric infectious diseases at Seattle Children’s Hospital, previously told HuffPost: “You have to try different doses to see which dose you really need.”

Now that Pfizer appears to be on the precipice of being able to distribute its vaccine to younger children, here’s what parents need to know:

Kids 5 to 11 get a dose that’s one-third the size given to adults.

First, it is important to remember that children under the age of 12 are not yet eligible for any of the three COVID vaccines currently available to teens and adults in the U.S.

The Pfizer vaccine is the furthest along, with the company recently announcing that a lower dose of its vaccine is both safe and effective in kids age 5 to 11. The Food and Drug Administration has said it expects the company to submit a request for emergency use authorization soon and is holding Oct. 26 for an advisory committee meeting to discuss the matter.

That suggests, therefore, that kids could start rolling up their sleeves in a matter of weeks.

If and when that happens, they’ll get a dose that’s one-third of the size given to teens and adults — and they’ll also need to receive two shots.

Adults receive two 30-microgram doses, so children ages 5–11 would receive two 10-microgram doses. (Pfizer is currently studying an even smaller dose in children under age 5. Those are unlikely to be eligible until 2022.)

Moderna hasn’t yet published any findings from its trial in younger children, though it’s also studying a lower dose.

The smaller dose is not based solely on kids’ size.

Researchers “are taking into account the typical age-related weights and how the medicine will distribute through the body,” Dr. Frank Esper, a pediatric infectious diseases specialist at Cleveland Clinic Children’s, told HuffPost.

But that’s not the only factor, he explained. Trial researchers (he is not one) were also accounting for the fact that children’s immune systems are different than those of adults.

Indeed, pediatric experts often emphasize that children are not just little adults from a physiological perspective. And the pandemic has made that clear. Kids are much less likely to become severely ill with or die from COVID-19, and their immune systems likely have much to do with that — though experts are still studying why and how.

If your child isn’t old enough for a vaccine yet ... wait.

While many parents are skeptical of vaccinating their children, others have been counting down the minutes until they’re eligible. But Esper cautioned against getting, say, an 11.5-year-old an adult-size dose of the vaccine now. Or getting a 10-year-old who is adult-size an adult-size shot.

“While you may have an adult-size 10-year-old, that doesn’t necessarily mean the immune system is adult-size,” he said, emphasizing again that the trials in children have been focused largely on dosing and safety.

Researchers “basically said all 5- to 11-year-olds got this dose — and we’ve made sure this dose is safe in 5 to 11-year-olds,” Esper said.

Of course, pediatricians and other primary care physicians have been watching all of this carefully, so if you have any questions about your child or their particular circumstances, now is a really good time to reach out, experts say.

As Dr. Mundeep Kainth, a pediatric infectious disease specialist from Cohen Children’s Medical Center in New York, previously told HuffPost: “If you have any concerns, or hesitancy, or just plain old ‘I want to understand more’ type of questions, this would be the time to reach out.”

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.

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