Research shows that children 3 years old and up are well-protected in both harness seats and booster seats. However, the American Academy of Pediatrics (AAP) recommends that children use a harness seat for as long as possible until they outgrow it. Maximum weights for harness seats range from 40 to 65 pounds, and even higher.
When a child has outgrown their harness seat, which usually occurs at about 4 years of age or higher, a booster seat is appropriate. Both backless and high-back booster seats have been found to provide good protection.
Every child is different. Please talk with your child’s doctor at each visit about which child restraint type is best for your particular child and circumstances.