Yes. The number of cases has been increasing over the past 30 years, especially in teens and infants younger than 5 months. In 1976, there were just over 1,000 cases of pertussis in the United States; in 2007, there were 10,000 cases. The reasons for this may include:- Infants are not fully protected against the disease until they have received at least three of the five doses of the DTaP vaccine, leaving them vulnerable to infection from unvaccinated children or adults.
- Some parents choose not to vaccinate their children with DTaP or other vaccines.
- Teens and adults whose DTaP vaccine has worn off and have not received Tdap, the booster vaccine, are contracting whooping cough and spreading it to others.
- Symptoms in teens and adults may not be diagnosed as whooping cough, so infected people unknowingly pass the illness to others.