RESUMO
AIM: The aim of our study was the long-term evolution of hepatitis B immunity and the titers of antibodies against the surface antigen (anti-HBs) acquired either naturally or after vaccination in hemodialysis (HD) patients with no history of hepatitis C virus (HCV) infection. METHODS: 36 HD patients were vaccinated with 4 doses of 40 microg recombinant B vaccine (Engerix, Rixensart, Belgium), intramuscularly at 0, 1, 2 and 6 months. 21 patients (60%) seroconverted developing anti-HBs titers > or = 10 IU/ml. Two patients were transferred to another unit before completion of 6 months after the last vaccine dose. We followed-up 19 HD patients who were immune against HBV after vaccination (Group A), and 30 immune patients (anti-HBs titers > or = 10 IU/ml) who had never been vaccinated and had antibodies against the core antigen (anti-HBc), diagnostic of natural HBV infection (Group B). In all patients of Groups A and B, anti-HBs were determined every 6 months, starting 6 months after the last dose in the vaccinated patients. Follow-up period lasted from October 2002 - April 2006. RESULTS: The mean follow-up in Group A was 21 +/- 12 months (range 6 - 36) and in Group B 29 +/- 12 months (range 6 - 42). Age, sex, presence of diabetes mellitus and duration of dialysis did not differ between the two groups. Five patients in Group A (26%) and 2 patients in Group B (9%) lost immunity (anti-HBs < 10 IU/ml) (p = 0.07). The median time to loss of immunity in Group A patients was 12 months (interquartile range 6 - 18 months), while in Group B patients it was 15 months (interquartile range 12 - 18 months). No booster dose was administered during the study. The 2 patients of Group B who lost immunity were the oldest of the group and redeveloped anti-HBs 6 and 12 months after they had lost it. During the first 6 months of the follow-up period, Group A had significantly higher anti-HBs titers than Group B (p < 0.05). However, this difference was lost later on, and after the first year of follow-up, anti-HBs titers were decreased significantly in Group A (p < 0.05), but remained unchanged in Group B throughout the follow-up period. CONCLUSIONS: In conclusion, HD patients lost hepatitis B immunity both after natural infection or vaccination, but naturally infected patients easily redeveloped protective anti-HBs titers. Anti-HBs titers decreased faster in vaccinated patients than in those with natural acquired immunity who held stable titers for a longer period. It is suggested that HD patients should be followed-up regularly for loss of HBV immunity after vaccination and receive a boosting dose when this occurs. In contrast, patients who acquired natural immunity do not need any anamnestic vaccination.
