PERSISTENCE OF IMMUNE RESPONSE AFTER HEPATITIS B VACCINATION IN MEDICAL STUDENTS AND RESIDENTS

BACKGROUND—Among the many high risk groups, medical students and residents are especially at risk for hepatitis B virus (HBV) exposure. HBV vaccination is a well-recognized preventive strategy but there is still uncertainty about the duration of protection and revaccination need. The aim of this study was to determine the anti-HBs antibody titer using ELISA method in the years after last dose of vaccine injection. MATERIALS AND METHODS—One hundred and fifty healthy medical students and residents who were training at Kerman University of Medical Sciences hospitals from September 2001 until September 2002, received three standard doses of recombinant HBV vaccine. For a time interval of 1, 2 – 5, and 5 – 10 years after last inoculation, the subjects were divided into three groups of 50-persons each. RESULTS—The subjects were 85 men and 65 women with a mean age of 26.8 ± 4 years. Overall, the mean of anti-HBs antibody titer was 1,766.7 ± 227.1 IU/L with minimum end of zero and maximum level of 10,500 IU/L. Based on the time lapsed since last inoculation the mean titer of anti-HBs antibody at the end of 1 year, 2 – 5, and 5 – 10 years were 3,446.8 ± 497.4, 1,603 ± 338.6 and 250 ± 59.3 IU/L, respectively (p < 0.001). Protective level of antibody ( > 10 IU/L) at the end of one year was seen in 98% of vaccinees. It declined to 94% in 2 – 5 year interval and to 84% in 5 – 10 years after inoculation. Most of the non-responders with antibody titer < 10 IU/L (8/12) were in the time interval 5 – 10 years. CONCLUSION—For a revaccination schedule among medical students and residents, we suggest anti-HBs antibody detection at 5 – 10 years after primary vaccination. Revaccination should be arranged due to personal need instead of whole target population.