Serum specimens were obtained from all subjects in the adolescent and adult acellular pertussis (aP) vaccine efficacy trial before and after immunization to study the prevalence of IgG and IgA antibody and geometric mean titers to 4 Bordetella pertussis antigens. Of 1793 adolescents and adult subjects who received aP vaccine, only 20%, 68%, 59%, and 39% had concentrations of IgG antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae types 2 and 3, respectively, that were greater than or equal to the limit of quantitation of the enzyme-linked immunosorbent assay used in the analysis. There was minimal variation in antibody prevalence with respect to geographic area, age, sex, or race.