Duration of immunity after hepatitis B vaccination: efficacy of low-dose booster vaccine.

Although the efficacy of hepatitis vaccine is well documented, the duration of immunity of healthy adults after vaccination is unknown. We studied 245 hospital employees 3 years after primary vaccination with hepatitis B vaccine to determine the prevalence of immunity indicated by levels of antibody to hepatitis B surface antigen of 10 mIU/mL or greater; and to compare the immunogenicity of low-dose intradermal vaccine with standard-dose intramuscular vaccine in persons found to be seronegative. Thirty-eight percent of employees studied had antibody levels less than 10 mIU/mL. Low levels were associated with smoking, older age, and higher body-mass index. Seventy-eight percent of persons with low antibody levels responded to a single booster vaccine. Two micrograms of intradermal vaccine was as effective as 20 micrograms of intramuscular vaccine in inducing an antibody response; however, intradermal vaccine was associated with more local reactions (42% compared with 17%). Many healthy adults will need periodic boosters of hepatitis B vaccine to maintain production of antibody to hepatitis B surface antigen; low-dose intradermal booster schedules may be feasible.