Study objectives: The incidence and prevalence of pertussis in adults have increased in recent years. It has been shown that previously immunized adults and adolescents are the main sources of transmission of Bordetella pertussis. The aim of this study was to describe the clinical presentation and the clinical course of pertussis in children and young adults who were immunized previously against B pertussis.
Design: Retrospective study.
Subjects: Children and young adults who were reported by local physicians to the Department of Epidemiology in the Israeli Ministry of Health with serologically confirmed pertussis and who were immunized previously were included. Information sought included personal data, epidemiologic data, signs and symptoms, laboratory results, initial diagnosis, and treatment.
Results: In the 95 previously immunized patients with serologically confirmed pertussis (mean age [+/- SD], 8.9 +/- 4.4 years old; range, 5 to 30 years old), the mean duration from onset of symptoms until the final diagnosis of pertussis was 23 +/- 15 days. The disease was usually atypical and generally mild. All the described patients had cough, usually prolonged, lasting 4 +/- 3.6 weeks. Only 6% had the classic whoop. The mean WBC count was 8.7 +/- 2.6 cells/mm6, and the lymphocyte count was 40 +/- 12%. Two patients were admitted to the hospital for severe pneumonia. Among the reported cases, the proportion of patients between the ages of 10 and 45 years increased from 6.5% during the period from 1971 to 1980, to 26% during the period from 1980 to 1990, and to 38% during a 1989 outbreak.
Conclusions: Pertussis in previously immunized individuals is usually characterized by an atypical and relatively mild clinical course. Patients suffer mainly from a prolonged and persistent cough. Early diagnosis may lead to prompt administration of therapy. Prophylaxis of exposed persons might be effective in decreasing both severity and transmission of the disease.