Diphtheria vaccine is a toxoid prepared by inactivating (with formaldehyde) the externally released toxin produced by Corynebacterium diphtheriae, the causative agent of diphtheria. Administration of three or more doses of diphtheria toxoid at intervals of six weeks or longer induces circulating antibodies that will protect against the toxic effects of diphtheria for several years. These toxic effects include damage to the nervous system or to the heart. Booster doses at intervals of ten years will maintain protective levels of circulating antibodies. Because the vaccine does not contain antigens from the bacterium itself, it will not prevent colonization or infection by C. diphtheriae. Diphtheria
ALAN R. HINMAN
Centers for Disease Control and Prevention (1991). "Diphtheria, Tetanus, and Pertussis: Recommendations for Vaccine Use and Other Preventive Measures. Recommendations of the Advisory Committee on Immunization Practices (ACIP)." Morbidity and Mortality Weekly Report 40:1–28.