Seroprevalence of pertussis antibodies among adolescents in Israel

Background: There is an increasing number of reports of pertussis among older children and adults. The development and licensure of an acellular pertussis vaccine offer the possibility of adult vaccination against the disease. Information on immunity to pertussis in this age group is needed before any vaccination policy can be considered. Objectives: To study the seroepidemiology of pertussis antibodies in a random sample of adolescents. Methods: Serum IgG antibodies to whole-cell lysate of Bordetella pertussis were measured by enzyme-linked immunosorbent assay in sera of 533 Israeli military recruits aged 17-18 years. Epidemiologic variables were collected by a questionnaire and analyzed for correlation with pertussis antibodies. Results: Of the sera tested 58.6% were positive for pertussis IgG antibodies, while 35.4% were negative and 6% were borderline. The seropositivity rate was significantly higher among females and non-smokers than among males and smokers. Serum samples of subjects found negative to Bordetella pertussis on recruitment were tested again, using the same ELISA assay, 2-3 years later. Seroconversion during the 3 year military service was detected in 12.5% of 40 subjects. Using the pertussis toxin as the antigen in a subsample of 160 sera, the seroprevalence was lower than that detected by the whole-cell lysate on the same sera (45% vs. 58%). Conclusions: A significant part of the adolescent population in Israel has low titer of serum IgG antibodies to the multiple antigens of B. pertussis. The relatively low concentration of anti-pertussis antibodies, together with the serological evidence of exposure to the disease indicates that booster immunization with the acellular pertussis vaccine of military recruits should be considered after more information on the incidence of clinical cases of pertussis will be available.