stylistic:tone, information:classification, information:extraction
Epidemiology

Before vaccines, an average of 178,171 cases was reported in the U.S., with peaks reported every two to five years; more than 93% of reported cases occurred in children under 10 years of age. With the widespread introduction of the DTP combined vaccine (diphtheria tetanus and pertussis) in the 1940s, pertussis incidence fell dramatically to approximately 1,000 by 1976, when they fluctuated between 1,000 and 30,000 annually.