l297 Pertussis in Massachusetts, 1981-1991: Incidence, Serologic Diagnosis, and Vaccine Effectiveness

Massachusetts provides diphtheria-tetanus toxoid-pertussis (DTP) vaccine, and since 1980 has monitored pertussis with a statewide diagnostic service. The incidence of bacteriologically confirmed pertussis was 104.5 per 100,000 person-years in I-month-old infants and declined progressively thereafter. Infants <6 months old experienced disproportionate morbidity: 44 % of bacteriologically confirmed pertussis, 64 % of hospitalizations, and 71 % of hospital days. Most children with pertussis had received <3 DTP doses during childhood, whereas 87 % of adoles-cents with pertussis had received ~4 doses. Serodiagnosis by single serum anti-pertussis toxin antibody ELISA increased the incidence of confirmed pertussis in persons 11-19 years old from 3.0 to 12.9 per 100,000 and in persons ~20 years old from 0.16 to 0.56 per 100,000. Bacterio-logic methods underestimate pertussis incidence, but a single serum anti-pertussis toxin anti-body ELISA is a practical method for population-based diagnosis in adolescents and adults. Universal immunization of infants and children with whole cell pertussis vaccine began in the 1950s in the United States and Britain and was followed by decline in pertussis incidence and mortality of> 1DO-fold [1, 2]. Although thes