Evidence for transmission of pertussis in schools, Massachusetts, 1996: epidemiologic data supported by pulsed-field gel electrophoresis studies.

In 1996, 18 of 20 pertussis outbreaks reported in Massachusetts occurred in schools. Pertussis surveillance data were reviewed and a retrospective cohort study was conducted in a high school that experienced an outbreak. Bordetella pertussis isolates from 9 school cases and from 58 cases statewide were examined by use of pulsed-field gel electrophoresis (PFGE). Statewide incidence rates were highest among children aged <1 year, 10-14 years, and 15-19 years (106, 117, and 104 cases per 100,000, respectively). Among 34 confirmed and 20 probable cases at the school, 61% had cough onset within 8 weeks of school opening. Five different PFGE types were identified among the 58 B. pertussis isolates from throughout the state. All 9 isolates from the affected high school were the same PFGE type. School-aged children may play an important role in pertussis epidemics. Consideration should be given to use of acellular pertussis vaccines among school-aged children.