What is the difference between the COVID-19 vaccines for kids and adults?

Michigan and the U.S. are entering a new phase in their battle with the pandemic after a Centers for Disease Control and Prevention committee gave its unanimous approval for a COVID-19 vaccine that can be given to young kids to protect them against the virus. 

Children age 5-11 are now offered protection against the virus, a demographic that had until this week, only masks and social distancing to use as their main form of defense.

According to Beaumont's Chief of Pediatric Infectious Disease, the Pfizer-BioNTech vaccine is 90% effective at preventing symptomatic cases of COVID-19 in kids 5-11.

There are a few key differences between the version now offered to children and those that have been administered to teens and adults. Most notably is the dosage, which is one-third the strength of the adult version. It is intended to be a two-shot regiment taken three weeks apart. 

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The shot that adults receive is 30 micrograms of RNA, whereas the shot intended for kids is only 10 micrograms. It's possible that even younger kids could someday receive the same vaccine with an even smaller dosage.

According to Pfizer, the lower dose was chosen to minimize the side effects exhibited by the shot but still provide strong immunity. 

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"If you're using an antibiotic or any other chemotherapy, those doses are dependant on weight factors," said Dr. Bishara Freij, the pediatric infectious disease chief at Beaumont. "Vaccine responses are due to the immune system identifying what's been injected. It will process the product then start forming antibodies that are independent of the shot."

Children typically produce a stronger immune system compared to adults. That's why they often don't need the same number of shots as older teens or adults for other viruses. And yet, smaller dosages can still produce effective or even more effective immune responses in kids compared to adults. 

Pfizer tested four different vaccine doses on 2,268 kids ages 5-11: 3 micrograms, 10 micrograms, 20 micrograms, and 30 micrograms. The clinical trials showed the 10-microgram dose had the most comparable effect in kids' antibodies to what the 30-microgram dose did for teens and adults.