Although it's considered a vaccine-preventable disease, whooping cough (pertussis) certainly hasn't been eliminated as a public health problem. The incidence of whooping cough has decreased by more than 90% over the last 70 years, but there are still outbreaks. While most other diseases that are vaccinated against in childhood are decreasing in frequency, cases of whooping cough have actually increased since 1990. This is likely due to the lower effectiveness of older vaccines (due to the emergence of new strains of the bacteria that causes the disease), decreased protection from the disease (immunity) in adults and adolescents as the effect of the vaccine wears off, parents opting out of vaccinating their children, and increased reporting of whooping cough by doctors.
Between 1,000 and 3,000 people each year get sick from pertussis. In Canada, 1 to 4 Canadians die each year from whooping cough. In unvaccinated populations, most cases occur in children under 5, especially in babies less than 6 months old. Because the effects of the vaccination wear off, adults are also susceptible to the disease. Those who have had the disease in the past may get it again, but it is usually a mild form which may go unrecognized and undiagnosed.