No, the Pfizer COVID-19 vaccine dosage is not the same for kids ages 5 to 11 as it is for adults

UPDATE Nov. 2, 2021:

The Centers for Disease Control and Prevention (CDC) has recommended a lower dose of Pfizer's COVID-19 vaccine for children ages 5 to 11. It's the first COVID-19 vaccine the CDC has recommended for a group of children younger than 12.

The CDC's recommendation comes after the Food and Drug Administration (FDA) on Oct. 29 authorized the emergency use of the Pfizer COVID-19 vaccine for children ages 5 to 11.

The FDA said it reviewed a study and conducted its own analysis that showed the vaccine was 90.7% effective in preventing COVID-19 in children ages 5 to 11.

Under the emergency use authorization, children ages 5 to 11 can receive two doses of the vaccine three weeks apart -- the same regimen as all other Pfizer COVID-19 vaccine recipients. But the vaccine dose for children ages 5 to 11 is 10 micrograms, which is one-third of the dose given to people 12 and older. You can read more below about why the vaccine dose for young children can be smaller and still be effective.

Original story from Sept. 22, 2021:

Pfizer made headlines on Sept. 20 when the company announced its study showed its COVID-19 vaccine is safe and effective for children ages 5 to 11. The company didn’t release the full data from its study but will submit the data to the U.S. Food and Drug Administration (FDA) when it applies for emergency use authorization. Pfizer says it plans to do that as soon as possible.

The announcement comes as many parents with children younger than 12 eagerly await a vaccine to help protect their kids against COVID-19. The American Academy of Pediatrics said there were nearly 226,000 child COVID-19 cases during the week of Sept. 9 to Sept. 16, the third-highest number of weekly cases during the pandemic.

A question people on social media had about the Pfizer COVID-19 vaccine was if the dosage for young children was the same as it is for adults.

THE QUESTION

Is the Pfizer COVID-19 vaccine dosage the same for kids ages 5 to 11 as it is for adults?

THE SOURCES

• Pfizer
• Dr. Aaron Milstone, pediatric infectious disease physician at Johns Hopkins Hospital
• Dr. Syra Madad, infectious disease epidemiologist in New York City and fellow at Harvard Kennedy School’s Belfer Center

THE ANSWER

No, the Pfizer COVID-19 vaccine dosage for kids ages 5 to 11 is not the same as it is for adults. During clinical trials, kids between 5 and 11 received one-third of the dosage adults receive.

WHAT WE FOUND

People 12 and older who are already eligible to receive a Pfizer COVID-19 vaccine get two doses of 30 micrograms. Each dose is ideally given 21 days apart.

In its news release about its trial results, Pfizer said a two-dose regimen of 10 micrograms per dose given 21 days apart was effective for children ages 5 to 11.

Dr. Aaron Milstone, a pediatric infectious disease physician at Johns Hopkins Hospital, said children’s immune systems respond differently than adults – therefore the vaccine can still be effective even with a smaller dose.

“What we learned from Pfizer is that what they're proposing is to use a lower dose than was given to adults, because you only need enough of the vaccine, or the amount of material in the vaccine, to get the body to respond,” he said. “And because kids have such a robust immune system and their ability to respond to that stimulus is so great, they found they can use a lower dose, which is optimistic.”

Milstone said other vaccines, including those for the flu and chickenpox, have varying doses as well depending on age.

“We want to give as little amount as we can to stimulate and awaken the immune system without causing those uncomfortable reactions,” he said.

Dr. Syra Madad, an infectious disease epidemiologist in New York City, said one of the purposes of clinical trials is to determine what dosage is appropriate.

Pfizer said 2,268 children ages 5 to 11 received a two-dose regimen of 10 micrograms each in its study. Those children generated an immune response and had side effects similar to what people ages 16 to 25 experienced with a 30-microgram two-dose regimen in a previous study, Pfizer said.

It’s still not clear when the Pfizer COVID-19 vaccine may be available to children ages 5 to 11. Madad noted Pfizer still needs to submit the results of its study to the U.S. Food and Drug Administration (FDA).

“Once the FDA gets that application, it could take anywhere from three to six weeks to review the data,” she said. “And then, you know, the CDC would then have to opine on it, and then the vaccine rollout would occur.”

Madad estimated the vaccine may be available for children ages 5 to 11 by the end of October or sometime in November. 

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