BACKGROUND: The incidence and prevalence of Hepatitis B virus (HBV) infection had decreased significantly in longterm hemodialysis (HD) patients. However, Seroconversion rates in response to HBV vaccine are poor in the HD population compared with the general population (35-80% vs above 95%) and the duration of immunity is shorter. The purpose of this study was to determine the association between hepatitis B immunity with HBsAb titer and variable dialysis-related factors as well as inflammation in HD patients. METHODS: The clinically stable 65 patients maintained on thrice weekly HD were divided into two groups according to their previous vaccination (V+group) or others (V-group). In V+group (n=25), patients with HBsAb titer less than 50 IU/L were administered a single dose of 40 microgram of IM HBV vaccine as a booster dose. Patients who lost immunity (defined as Ab titer decreasing to <10 IU/L) after the booster were administered a course of intradermal (ID) vaccination. In V-group (n=40), patients with natural acquired immunity (Ab titer > or =10 IU/L, N=31) were followed over 12 months in our center. V-group without natural immunity (n=9) received three doses of IM HBV vaccination (40 microgram). RESULTS: Most (90%) of vaccinated patients at pre-dialysis period had persistent immunity. Booster at HBs Ab titer below 10 IU/L had significantly shorter duration of immunity. Increase of (delta)hsCRP between pre & post-booster was significantly related to the loss of immunity. Based on multivariate logistic analysis, the subset of variables best explaining seroconversion after booster was lower (delta)hsCRP and younger age. Seroconversion rate to ID vaccination was 66.7%. Non-diabetes, higher hematocrit & low rHuEpo dose were implicated as having a role in maintaining strong naturally acquired immunity (Ab titer> or =100 IU/L) (p<0.05). Patients with weak naturally acquired immunity had increased median hsCRP than patients with strong. Seroconversion rate to conventional IM vaccination was 66.7%. CONCLUSION: We suggest that tailored modification of strategies about hepatitis B is required to persist protective immunity in hemodialysis patients before too late until loss of immunity, HBsAb titers below 10 IU/L. Also, our study implicated patients with prolonged and strong immunity against HBV may be related to higher hematocrit, better adequacy of dialysis and low inflammatory state, which all associated with better cardiovascular outcome and survival in hemodialysis patients.