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Why is the COVID vaccine dose based on age versus weight?

Pediatricians and other experts answer questions about the COVID-19 vaccines.

Infectious disease epidemiologist Jessica Malaty Rivera, MS explains why kids ages 5-11 get a lower dose COVID-19 vaccine than those 12 and up.

I think a lot of times people confuse the fact that often times medication is dosed based on body size and based on weight because of how the body can metabolize that. Vaccines are very small when you think about it, and it’s just an introduction to an antigen basically telling your immune system to look out for something. So that dosage is not huge to begin with. And we know that we want the immune system or the age of that person to be at a certain point before we can give them a certain dose.

And so, that’s why when you look at the pediatric vaccine schedule it’s based on the child’s age not their weight. And the same way for the COVID-19 vaccine, it’s based on the child’s age. Most pediatricians would say, if you have a child who is small for their age it’s still fine to get whichever vaccine they are eligible for based on their birthday. Now, if you have a kid who’s on the cusp of birthdays in between that, the recommendation is to get the dose that is available to you at the point of that child’s age.

This information is shared for educational purposes only and should not be used as a substitute for professional medical advice. The views expressed are those of the featured medical professional and reflect information available to that professional at time of filming. Always consult a health care provider for any personal health decisions. Click here for vaccine FAQs from the CDC.

Stay up to date with your COVID vaccine, including boosters!

COVID vaccines are safe and effective for everyone ages 6 months and older.

Immunity wanes over time. Keep up your protection against COVID by getting boosted when eligible.

Updated (bivalent) boosters are now available for adults and children 6 months and older.