PERTUSSIS IN MASSACHUSETTS, 1981-1991 - INCIDENCE, SEROLOGIC DIAGNOSIS, AND VACCINE EFFECTIVENESS

Massachusetts provides diphtheria-tetanus toxoid-pertussis (DTP) vacci ne, and since 1980 has monitored pertussis with a statewide diagnostic service. The incidence of bacteriologically confirmed pertussis was 1 04.5 per 100,000 person-years in 1-month-old infants and declined prog ressively thereafter. Infants <6 months old experienced disproportiona te morbidity: 44% of bacteriologically confirmed pertussis, 64% of hos pitalizations, and 71% of hospital days. Most children with pertussis had received <3 DTP doses during childhood, whereas 87% of adolescents with pertussis had received greater than or equal to 4 doses. Serodia gnosis by single serum anti-pertussis toxin antibody ELISA increased t he incidence of confirmed pertussis in persons 11-19 years old from 3. 0 to 12.9 per 100,000 and in persons greater than or equal to 20 years old from 0.16 to 0.56 per 100,000. Bacteriologic methods underestimat e pertussis incidence, but a single serum anti-pertussis toxin antibod y ELISA is a practical method for population-based diagnosis in adoles cents and adults.