Your Healthy Family: Why dosing for kids' COVID-19 vaccine is by age, not weight

Posted at 7:24 AM, Nov 02, 2021
and last updated 2021-11-02 07:27:45-04

Pfizer's COVID-19 vaccine is getting closer to being available for kids ages 5-11. Many parents are wondering why dosing for the shot is based on a child's age and not their weight.

The shot for younger kids would be given in two doses, 21 days apart. Each dose will be just a third of the size of the one given to people 12 and older.

"Vaccines are not administered based weight like other therapeutics are,” Dr. Chris Pernell, a Public Health Physician, said.

Dr. Pernell said the dosage size varies depending on a child's immune system.

"Vaccines really are based on the developmental stage, or age of the immune system in a younger person. That's why you see the differences in the cut offs of the ages," She said.

Trials have shown the two smaller doses of Pfizer's COVID-19 vaccine led to just as strong of an immune response in kids as the larger doses do in people over 12.

Dr. Pernell said parents of young children shouldn't worry about the size of the doses.

"A parent who has an 11-year-old, regardless of size, your 11-year-old should receive the authorized dose for that stated age," she said.

Pfizer has packaged separate vials of the vaccine for kids 5-11, which have orange labels. Purple labels are being used for vaccines for people ages 12 and older.