Corynebacterium diphtheriae may cause both localized and generalized disease. Systemic intoxication is caused by diphtheria exotoxin, an extracellular protein metabolite of toxigenic strains of C. diphtheriae. Protection against disease is due to the development of neutralizing antibodies to diphtheria toxin.

At one time, diphtheria was common in the United States (US).More than 200,000 cases, primarily among young children, were reported in 1921.Approximately 5% to 10% of cases were fatal; the highest case-fatality ratios were recorded for the very young and the elderly. Reported cases of diphtheria of all types declined from 306 in 1975 to 59 in 1979; most were cutaneous diphtheria reported from a single state. After 1979,cutaneous diphtheria was no longer a notifiable disease. From 1980 to 1989,only 24 cases of respiratory diphtheria were reported; two cases were fatal, and 18 (75%) occurred among persons 20 years of age or older.²

Diphtheria is currently a rare disease in the US primarily because of the high level of appropriate vaccination among children (97% of children entering school have received ≥three doses of diphtheria and tetanus toxoids and pertussis vaccine adsorbed [DTP]) and because of an apparent reduction in the prevalence of toxigenic strains of C. diphtheriae. Most cases occur among unvaccinated or inadequately immunized persons.²

Both toxigenic and nontoxigenic strains of C. diphtheriae can cause disease, but only strains that produce toxin cause myocarditis and neuritis. Toxigenic strains are more often associated with severe or fatal illness in noncutaneous (respiratory or other mucosal surface) infections and are more commonly recovered in association with respiratory than from cutaneous infections.²

A complete vaccination series substantially reduces the risk of developing diphtheria, and vaccinated persons who develop disease have milder illness. Protection lasts at least 10 years. Vaccination does not, however, eliminate carriage of C. diphtheriae in the pharynx or nose or on the skin.²

Protection against diphtheria and tetanus can be provided by circulating protective levels of diphtheria and tetanus antitoxin which can be induced by the administration of Diphtheria and Tetanus Toxoids Adsorbed USP (For Pediatric Use) (DT).

A clinical study was performed in 20 children under one year of age to determine the serological responses and the adverse reactions when Aventis Pasteur Inc.(AvP) DT was administered as a primary series of three doses. Protective levels of diphtheria and tetanus antitoxins (0.01 AU/mL) were detected in 100% of the children following two doses of the vaccine. However, maternal antibody may have contributed to the total neutralizing antibody in some of these infants. Protective levels of antitoxin were observed in 100% of these infants following three doses of DT. No local or systemic reactions were observed in approximately half of the infants and only mild or moderate reactions were observed in the remainder of the DT study group.(Table 1)³

TABLE 1³ NUMBER (PERCENT) OF CHILDREN PROTECTED FOLLOWING ADMINISTRATION OF DT

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