<P> 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 . The actual incidence was likely much higher . After vaccinations were introduced in the 1940s , pertussis incidence fell dramatically to approximately 1,000 by 1976 . Incidence rates have increased since 1980 . In 2015 , rates in the United States were 20,762 people . </P>
when did they start vaccinating for whooping cough
the 1940s