AbstractObjective:To evaluate the efficacy of giving a third dose of recombinant hepatitis B vaccine to healthcare workers who already had received two doses of serum-derived vaccine, which is no longer available in the United States.Design:Volunteers who already had received two standard 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 immunization, three months later, and one year after the third immunization.Setting:U.S. Army Medical Center, El Paso, Texas.Patients:One hundred healthy healthcare workers.Results:Three months after receiving the third immunization, the serum vaccine group had significantly higher titers than the recombinant vaccine group (P= 0.018). One year after receiving the third immunization, those who received the combined regimen had a mean hepatitis B surface antibody titer less than half that of those who received three doses of serum-derived vaccine. However, both regimens resulted in titers that are considered to confer immunity.Conclusions:A regimen that combines serum and recombinant hepatitis B vaccines may not produce as high an antibody level as three doses of the same vaccine. Those who began immunization with serum vaccine and concluded with recombinant vaccine should be monitored for an accelerated drop in serum antibodies.
