Outbreak of pertussis in a fully immunized adolescent and adult population.

OBJECTIVE

To evaluate the spread of pertussis in a fully immunized eighth-grade class and the household contacts of two coindex cases of pertussis.

DESIGN

Survey of infected subjects and their contacts was performed using culture, direct fluorescent antibody assay, and serological assays to establish the diagnosis of Bordetella pertussis.

SETTING

Middle-class parochial school.

PARTICIPANTS

A volunteer sample of 15 eighth-grade students and 13 household contacts of two identified cases of B pertussis infection.

INTERVENTIONS

All participants had medical histories (including immunization status) and laboratory evaluation for B pertussis infection (including nasopharyngeal specimens and serum samples) obtained initially and 30 days later. After initial evaluation, all subjects received erythromycin ethyl succinate therapy.

MAIN OUTCOME MEASURES

Assessment of B pertussis infection as defined by positive nasopharyngeal culture, direct fluorescent antibody, or serological tests.

RESULTS

Laboratory evidence of B pertussis infection was found in eight (47%) of 17 immunized eighth-grade classmates and in three (23%) of 13 household contacts, all of whom were 12 years of age or older.

CONCLUSIONS

Vaccine-induced immunity wanes by early adolescence. These older age groups may be infected with B pertussis and may serve as reservoirs of infection for other susceptible individuals.