Serum antibodies against a 69-kilodalton outer-membrane protein, pertactin, from Bordetella pertussis in nonvaccinated children with and without a history of clinical pertussis.

Serum antibodies against pertactin were found in all samples from 260 nonvaccinated healthy Swedish 1- to 4-year-old children, although 42% had neither a history of clinical pertussis nor antibodies against pertussis toxin or filamentous hemagglutinin. Pertactin antibody levels were, however, higher in children with a history of pertussis than in those without a history of pertussis, and higher in children with antibodies against pertussis toxin and filamentous hemagglutinin than in those without such antibodies.