In humans, serum and secretory IgA antibodies to antigens of B. pertussis are detected in convalescent sera and secretions, but not in sera or secretions from vaccinees. Parenterally administered vaccines, currently in use, elicit systemic but not mucosal immunity. Induction of a vigorous local immune response at the mucosal epithelium of the respiratory tract may provide superior protection against pertussis, in contrast to parenteral vaccines. Procedures have been developed to measure the following in saline and nasopharyngeal aspirants: total protein, total IgA and IgA to specific pertussis antigens (PT, FHA, pertactin and fimbriae). (1) The procedures were used to evaluate the mucosal response in individuals from Children's Hospital National Medical Center (project ZO1 BA-07004-03 LP). (2) These assays were performed on 50 individuals in a pilot study in Sweden designed to determine the optimal diagnostic assays to be used to evaluate cases in upcoming efficacy trials. Results will be compared with PCR and culture to define assay sensitivity and specificity.