This situation is mainly due to the fact that duration of disease or vaccine induced immunities are not life-long. It is now observed in highly vaccinated countries an increase of pertussis incidence in newborns too young to be vaccinated, contaminated by adolescents and adults previously vaccinated or infected whose immunity decreased with time. For this reason, France and other countries decided recently to add vaccine boosters for adolescents and adults.
Surveillance of the disease is of great importance in order to analyse the impact of such boosters on newborn mortality and morbidity and necessitates the use of biological diagnosis especially for previously vaccinated adolescents and adults with atypical clinical symptoms.