The dosage depends on the schedule and manufacturer of the vaccine that you are using. For children 11 through 15 years of age, the 2-dose Recombivax HB volume is 1.0 mL. Otherwise, the 3-dose schedule of Recombivax HB or Engerix B is 0.5 mL through age 19 years. Heplisav-B, the 2-dose HepB vaccine given with a 4-week interval between 0.5 mL doses, is licensed for adolescents and adults beginning at age 18 years. Immunize.org offers a handy resource with charts detailing the correct dosages and schedules for monovalent HepB and HepA vaccines and combination products that include HepA and HepB vaccines. Go to www.immunize.org/catg.d/p2081.pdf.