In September 1999, Merck Vaccine Division (Merck & Co., Inc., West
Point, Pennsylvania*) received approval from the Food and Drug Administration for
an optional two-dose schedule of Recombivax
HB® for vaccination of adolescents
aged 11--15 years. The Advisory Committee on Immunization Practices approved
the optional two-dose schedule in October 1999 and recommended to include
this schedule in the Vaccines for Children Program in February 2000. Using the
two-dose schedule, the adult dose of Recombivax
HB® (1.0 mL dose containing 10 µg of
hepatitis B surface antigen [HBsAg]) is administered to adolescents aged 11--15 years, with
the second dose given 4--6 months after the first dose. In immunogenicity studies
among adolescents aged 11--15 years, antibody concentrations and end seroprotection
rates (>10 milli-international units per mL of antibody to HBsAg) were similar with the
two-dose schedule (1.0 mL dose containing 10 µg of HBsAg) and the currently
licensed three-dose schedule (0.5 mL dose containing 5 µg of HBsAg). The overall frequency
of adverse events was similar for the two-dose schedule and the three-dose
schedule. Short-term (2-year) follow-up data indicate that the rate of decline in antibody
levels for the two-dose schedule was similar to that for the three-dose schedule. No data
are available to assess long-term protection (beyond 2 years) or immune
memory following vaccination with the two-dose schedule, and it is not known whether
booster doses of vaccine will be required. As with other hepatitis B vaccination schedules,
if administration of the two-dose schedule is interrupted it is not necessary to restart
the series. Children and adolescents who have begun vaccination with a dose of 5 µg
of Recombivax HB® should complete the three-dose series with this dose. If it is not
clear which dose an adolescent was administered at the start of a series, the series
should be completed with the three-dose schedule.
*Use of trade names and commercial sources is for identification only and does
not constitute endorsement by CDC or the U.S. Department of Health and Human Services.
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