title: Cumulative incidence of pertussis in an unvaccinated preschool cohort based on notifications, interview and serology.
abstract: The cumulative incidence of pertussis at six years of age in the first unvaccinated cohort after cessation of immunisation in Sweden was investigated by serological methods and by a validation of the national epidemiological surveillance system by reports from the Child Health Centres (CHCs). In 312/385 (81%) eligible children, both an interview with the parents and a blood sample from the child could be obtained. The CHC reports yielded a cumulative incidence of 31%, whereas the serological assays found 54%. Of the cases reported by the parents to the CHCs, 89% were seropositives. In the additional cases of pertussis reported at the study interview, only 61% could be confirmed (p less than 0.001). Among children with reported severe cough not suspected to be pertussis, 46% were seropositive, distributed as 33% seropositives in cases with cough duration of less than 4 weeks and 69% for longer coughs (p less than 0.01). In the CHC reports, the parental diagnosis was found to have been confirmed in three-quarters of cases by medical personnel. The CHC reporting system was thus found to be reliable with an observed specificity of 93%, but sensitivity of only 52%. Thus, even this surveillance system, which yields the highest incidence rates, underestimates the incidence of the disease.
authors.affiliation: Division of Child Health, Landstingets kansli, Jönköping, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Mark
authors.forename: M
authors.initials: M
authors.lastname: Granström
mesh_terms: D001886:Bordetella pertussis / Q000302:isolation & purification; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016358:Contact Tracing; D006801:Humans; D015994:Incidence; D007407:Interviews as Topic; D010567:Pertussis Vaccine / Q000008:administration & dosage; D016036:Seroepidemiologic Studies; D013548:Sweden / Q000453:epidemiology; D014917:Whooping Cough / Q000453:epidemiology* / Q000517:prevention & control
chemical_list: D010567:Pertussis Vaccine