Pertussis and the Red Queen Effect

Whooping cough is a contagious and typically childhood disease transmitted via droplets. Pertussis is especially dangerous for infants, but adults have become more susceptible. A pathognomonic symptom of pertussis is a severe spasmodic and unproductive cough that worsens at night and is accompanied by vomiting, apnea and cyanosis. The symptoms among vaccinated children, adolescents and adults, are milder, less characteristic, and therefore more difficult to diagnose. Whole-cell pertussis vaccine (DTwP) has been highly effective in reducing morbidity and mortality. However, in many countries DTwP vaccines, due to their reactogenicity, have been completely or partly replaced, by acellular pertussis vaccines (DTaP) that contain several purified bacterial protein antigens. In spite of the sustained high coverage of vaccinations, there is an increase of whooping cough cases in all age groups. The main cause of the increase is the lack of full protection from acellular vaccine in preventing transmission of Bordetella pertussis, which is the main etiological factor of whooping cough. Moreover, new diagnostic methods allow to identify other Bordetella species that cause pertussis-like symptoms, i.e. B. parapertussis and B. holmesii. The currently used vaccines do not provide a cross-protection against B. holmesii that has now become the second etiological factor of pertussis. Imperfections of existing vaccines are the reason for an intense development of improved anti-pertussis vaccines. Several research directions can be distinguished, such as identifying new components, designing an acellular vaccine based on the outer membrane vesicles or the renewed interest in whole cell vaccines.