Abstract
Objective: Blood exposure and subsequent blood-borne infections are major risk factors for acquired occupational diseases. Hepatitis B (HB) viral infection is among them, and it is well known that it causes cirrhosis and liver cancer in two or three decades. It can be prevented with HB vaccination, which is recommended for medical staff. However, the antibody titer for acquired immunization generally decreases with time. The authors investigated the time-dependent decrease in HB virus antibody titers after vaccination.
Methods: Three hundred and seventy-five (70 males and 305 females) hospital employees were immunized with HB vaccine at their workplace and thereafter when needed. HB virus surface antibody titers were measured in 2004, 2007, 2010 and 2015, using a semi-quantitative photo-hemagglutination assay. Measured titers were defined as negative for 8 times or less and positive for 16 times or more.
Results: Out of the total of 375 persons who had been injected with HB vaccine, there had been significant titer loss in 132 (35%) in five years. There was no significant statistical difference between two subgroups, one of them consisting of persons who had continued to have positive results and the other of persons who had newly obtained immunity. Conversion from a positive to a negative result was more likely in males than in females (50% vs 32%, p < 0.01).
Conclusions: The titers of approximately one-third of the subjects converted from positive to negative in five years. After HB vaccination, periodical antibody titer measurements and additional vaccination may be recommended for persons with negative results.
