Why does a 15-year-old who weighs 160 pounds receive a pediatric dose of HepA while his 110-pound mother receives an adult dose (twice the pediatric dose)?

The efficacy data from the clinical trials were based on age at time of vaccination, and not on the weight of the individual. Hence, the dosage recommendations reflect this age-based efficacy data. The same holds true for HepB vaccine. In addition, higher response rates are expected in younger people, even if their weights are above the norm.