EFFICACY OF IMMUNIZATION WITH A COMBINATION OF SERUM AND RECOMBINANT HEPATITIS-B VACCINES

OBJECTIVE: To evaluate the efficacy of giving a third dose of recombin ant hepatitis B vaccine to healthcare workers who already had received two doses of serum-derived vaccine, which is no longer available in t he United States. DESIGN: Volunteers who already had received two stan dard doses of serum-derived vaccine were given a third dose of either serum or recombinant-vaccine in a double-blind fashion. Antibodies to hepatitis B surface antigen were measured at the time of the third imm unization, three months later, and one year after the third immunizati on. SETTING: U.S. Army Medical Center, El Paso, Texas. PATIENTS: One h undred healthy healthcare workers. RESULTS: Three months after receivi ng the third immunization, the serum vaccine group had significantly h igher titers than the recombinant vaccine group (P = 0.0 18). One year after receiving the third immunization, those who received die combin ed regimen had a mean hepatitis B surface antibody titer less than hal f that of those who received three doses of serum-derived vaccine. How ever, both regimens resulted in titers that are considered to confer i mmunity. CONCLUSIONS: A regimen that combines serum and recombinant he patitis B vaccines may not produce as high an antibody level as three doses of the same vaccine. Those who began immunization with serum vac cine and concluded with recombinant vaccine should be monitored for an accelerated drop in serum antibodies.