Comparison of higher-dose intradermal hepatitis B vaccination to standard intramuscular vaccination of healthcare workers

OBJECTIVE: To compare the immunogenicity of hepatitis B vaccine administere d via intradermal (ID) versus intramuscular (IM) route. METHODS: Subjects chose either to specify the route of immunization or to u ndergo random allocation to vaccination by the ID (0.15 mt) or the IM (1.0 mt) route. Yeast-derived recombinant hepatitis B vaccine was given at 0, 30 , and 180 days. Hepatitis B surface antibody (HBsAb) and hepatitis B core a ntibody (HBcAb) were measured by microparticle enzyme immunoassay. RESULTS: 763 subjects were enrolled. Baseline screening identified 65 subje cts (8%) who were positive for HBsAb or HBcAb. Vaccination was completed by 590 (85%) of 698 enrollees (370 ID, 220 IM). Seroconversion rates (geometr ic mean titers [GMT]>0 IU/mL HBsAb) for those vaccinated ID were 99% and 96 % for screening at 9 months and 1 year post-vaccination, respectively; subj ects vaccinated intramuscularly had similar rates of 95% and 9676. Seroposi tivity rates (GMT greater than or equal to 10 IU/mL HBsAb) showed a similar pattern, with 95%, 92%. and 73% at 9 months and 1 and 2 years, respectivel y, for those vaccinated ID, and 94%, 93%, and 81% for those having IM vacci nation. GMT for HRsAB, was significantly higher for individuals vaccinated IM than for those vaccinated ID (P<.0001). The GMT ratio for the LM and ID routes decreased over time, being 9.3 at 9 months, 7.8 at 1 year, and 5.9 a t 2 years. An unanticipated side effect of intradermal vaccination was skin discoloration at injection sites, which persisted for at least 2 years pos tvaccination. Two thirds (112/166) of respondents reported that they would have selected the ID route despite the discoloration. CONCLUSIONS: Higher-dose ID vaccination (3 vs 1 mu g per injection) uses on e sixth of the dose required for standard IM vaccination. It is a cost-effe ctive way to vaccinate populations against hepatitis B virus. but the long- term efficacy of the ID route must still be investigated.