Despite having achieved very high vaccination coverage rates for over 30 years with a vaccine whose protective efficacy has been confirmed by surveillance data and outbreak investigations, pertussis has not been eliminated in France. Data from a multicenter hospital survey conducted in 1993–94, as well as data obtained through the Renacoq pediatric hospital surveillance network established following this study, 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 ten 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 into the French vaccination schedule of a pertussis booster shot at ages 11–13, based on the use of new acellular vaccines. The impact of this measure, particularly on the incidence of the disease in the first year of life, is being monitored by volunteer pediatricians and bacteriologists participating in the Renacoq network.