I was a member of the WHO committee and disagreed with the primary case definition because it was clear at that time that this definition would eliminate a substantial number of cases and therefore inflate reported efficacy values. 4–11 Nevertheless, the Center for Biologics Evaluation and Research of the Food and Drug Administration accepted this definition, and package inserts of the US-licensed DTaP vaccines reflect this.
Since the 1993 pertussis epidemic in Cincinnati occurred primarily among children who had been appropriately immunized, it is clear that the whole-cell pertussis vaccine failed to give full protection against the disease.[ii]