Serum IgA antibody to Bordetella pertussis as an indicator of infection.

The levels of pertussis-specific IgA antibodies in sera from vaccinees and from children with Bordetella pertussis infection were compared by an enzyme-linked immunosorbent assay (ELISA). Serum IgA antibodies were produced only after natural contact with the pathogen and, therefore, their presence can be used as an indicator of infection. However, in view of the relatively long interval between infection and the appearance of antibodies, and the prolonged antibody response, their presence cannot be used as proof of recent infection. The finding of these antibodies in a high percentage of the normal adult population may indicate a constant circulation of B. pertussis without symptoms of disease.