Despite having achieved very high vaccination coverage for over 30 years with a vaccine whose protective efficacy has been confirmed, pertussis has not been eliminated in France. Data obtained through the Renacoq pediatric hospital surveillance network and through investigations of clusters of cases have made it possible to characterize the current epidemiology of the disease and to understand the reason for the continued circulation of Bordetella pertussis. A duration of protection conferred by vaccination of approximately 10 years has led, in the absence of natural booster immunity due to reduced circulation of the wild-type bacterium, to the formation of a reservoir of susceptible older children and young adults. These individuals constitute, particularly in departments where vaccination coverage is highest, the main source of infection for very young infants before they have been protected by a full course of vaccination. This finding was the basis for the introduction, in 1998, of a pertussis booster shot at ages 11–13 into the French vaccination schedule, based on the use of new acellular vaccines. Monitoring of the impact of this measure in the first year of life is conducted by the Renacoq Network, and in the general population through investigations of clusters of cases.