An adolescent received the first dose of HepB at age 11 years but did not return for subsequent doses. If the patient comes back at age 16 years, is it necessary to repeat the first dose of the series?

It is not necessary to restart or add doses to the HepB series (or any other routine vaccine series) because of a prolonged interval between doses. Just continue the series from the point where it was interrupted. Note that the 2-dose Recombivax HB series using the adult formulation is approved only for adolescents 11 through 15 years of age. At age 16 years, the schedule reverts to the standard pediatric formulation 3-dose schedule rather than 2 adult doses.