In a previous study, we observed marked variation in the titer, avidity and longevity of IgG antibodies against diphtheria toxoid (DT), pertussis toxoid (PT), filamentous hemagglutinin (FHA), and pertactin (Prn) in 28 inbred strains of mice following vaccination with a licensed diphtheria-tetanus-acellular pertussis (DTaP) vaccine [26]. Here, CIAO3 is linked to pertussis.