Before pertussis vaccines became available in the United States, nearly a quarter of a million pertussis cases were reported each year. After whole cell DTP vaccine gained widespread use during the 1940s, reported cases fell dramatically reaching a low in 1976 of approximately 1,000 cases. Since 1976, reports of whooping cough have been on the rise. This observation can be explained, at least in part, by better awareness of pertussis illness beyond infancy, as many cases in older children, adolescents and adults don’t present in the classic manner of whooping cough. Instead, pertussis illness beyond infancy, especially in individuals who have previously been immunized, more characteristically presents as a prolonged cough illness. The concept that childhood vaccination does not provide lifelong immunity has only become well established in the last 20 years. Prior to routine pertussis vaccination, more than 90% of pertussis cases occurred in children <10 years of age.1 In 2014, approximately half of reported cases were in adolescents and adults.
The current pertussis vaccine schedule begins during infancy. The Advisory Committee on Immunization Practices (ACIP) recommends that children be immunized with their primary series, in the form of DTaP (diphtheria, tetanus, pertussis) at 2, 4, and 6 months of age with booster doses at 15–18 months, and 4–6 years. Between the ages of 11 and 12 years, a single booster dose, using the booster formulation Tdap, is given. While the antigens are the same as those found in the DTaP formulation of the vaccine, the amount of some of the antigens is reduced in the Tdap booster formulation. For anyone (adolescent through adulthood) who has not yet received a dose of Tdap, the ACIP recommends a single dose as ‘catch up‘.