Background: Pertussis is a highly communicable disease of the respiratory tract caused by Bordetella pertussis. Neither natural disease nor vaccination provide complete or life long immunity against reinfection or disease. Protection against typical disease is immeasurable after 12 years. Coughing adolescents and adults currently are the major reservoir for B. pertussis and are the usual source for “index cases” in infants and children. Without natural reinfection with B. pertussis or repeated booster vaccination, adolescent and adults are susceptible to clinical disease if exposed. The aim of this study was to assess the B. pertussis antibody levels in the medical students of Hamedan University of Medical Sciences. Methods: One hundred sixty-three first grade medical students with no history of chronic respiratory infection and immunodeficiency were selected. Serum samples were collected from them and analyzed for anti-pertussis toxin (PT) IgG antibodies by enzyme-linked immunosorbent assay (ELISA). Antibody titers were calculated using reference line methodology. Anti-PT titers more than 24 g/ml were considered to be positive. Results: The mean age of cases was 19.48 year. Out of 163 cases, 47.6 percent had positive antibody titer and the mean of antibody titer was 71.72 g/ml. 42% of females and 54% of males had positive antibody titers. Thirty-three percent of age group 21yr had positive antibody level. The mean of antibody level in male was 84.07, in female was 58.9 u/ml. Antibody levels were not statistically significantly different between males and females. The mean antibody level in age group 21 yr was 49.269 g/ml. There were no statistically significant differences between age groups in the proportion of antibody levels. Conclusion: The high rates of seropositivity in our study population indicate previous infection, which are a threat to infants who have not completed primary immunisation. In this respect, booster vaccination for adolescents and adults is recommended.
