Persistence of immunologic memory in long-term hemodialysis patients and healthcare workers given hepatitis B vaccine: role of a booster dose on antibody response.

Hepatitis B (HB) vaccine is effective in producing protection against HB virus infection, but the persistence of immunity remains largely unknown. Seventy-six hemodialysis (HD) patients (60 after primary HB vaccination and 16 with natural immunity) and 46 healthcare workers (32 after primary HB vaccination and 14 with natural immunity) were followed up for 10 years to evaluate the persistence of immunity. Ten years after vaccination, the analysis showed a lower seroconversion rate (38 vs. 75%, p < 0.001) in HD patients as compared with healthcare workers. In the follow-up period, the protective immunity developed through HB virus infection also showed a lower seroconversion rate (44 vs. 86%, p < 0.025) in HD patients as compared with healthcare workers. To assess the status of immunologic memory, we administered a booster dose of HB vaccine 3-12 years (mean 6.7 +/- 0.6 years) after primary vaccination in a selected group of 37 HD patients who presented a decline of their antibodies or were nonresponders. In another group of 12 healthcare workers who had a decline of their antibodies, we also administered a booster dose of HB vaccine 5-8 years (mean 5.8 +/- 0.3 years) after primary vaccination. Nineteen of the 37 HD patients (51%) presented an anamnestic response to the booster dose, and 15 of these (40%) were high responders. All of the healthcare workers responded to the booster dose with a high antibody response. We conclude that patients undergoing HD not only have lower rates of immunization to HB than healthy adults, but also that these are frequently transient. Booster doses after a primary course of vaccine are effective in about the half of HD patients who presented a decline of their antibodies or were nonresponders but whether they are necessary is unclear. The majority of healthcare workers continue to have high levels of protective HBs antibody for at least 10 years and routine boosters are not required.