Bordetella pertussis: why is it still circulating?

Bordetella pertussis is the causal agent of whooping cough, a highly contagious respiratory disease that is life-threatening in infants under the age of three months and may also be very severe in pregnant women and seniors. This disease can be prevented by vaccination but it remains a public health problem in many developed and developing countries.(1) So, why is B. pertussis still circulating? We need to consider several aspects of this vaccine-preventable disease when answering this question: (i) the history of the disease and the historical context in which the vaccine was developed; (ii) the type of vaccine used; (iii) the vaccination strategy and coverage; (iv) the disease surveillance after the introduction of generalized vaccination and (v) the surveillance for the causal agent of the disease.