CLINICAL PHARMACOLOGY
DIPHTHERIA
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 (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) can be provided by circulating protective levels of diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) antitoxin which can be induced by the administration of Diphtheria and Tetanus Toxoids Adsorbed USP (diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) toxoids) (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 (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) 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
| Post 2 Doses* | Post 3 Doses |
Diphtheria Antitoxin (> 0.01 units/mL) | 20/20 (100%) | 20/20 (100%) |
Tetanus Antitoxin (> 0.01 units/mL) | 20/20 (100%) | 20/20 (100%) |
*Maternal antibody may have contributed to a portion of the total antibody.
Another clinical study to evaluate serological responses and adverse reactions of AvP's DT was performed in 40 children under one year of age. One group of 20 children received 0.5 mL doses of DTP,DT,DTP at two, four and six months of age, respectively. The second group of 20 children received 0.5 mL doses of DTP, DTP, and DT, respectively, at the same ages.4
The immunologic protection as measured by toxin neutralization induced by DT was comparable when administered as either a second or third dose (TABLE 2).4
TABLE 24 NUMBER (PERCENT) OF CHILDREN PROTECTED FOLLOWING ADMINISTRATION OF THREE DOSES
Antibody | DTP,DT,DTP Group | DTP,DTP,DT Group |
Diphtheria Antitoxin (> 0.01 units/mL) | 18/18 (100%) | 19/19 (100%) |
Tetanus Antitoxin (> 0.01 units/mL) | 18/18 (100%) | 19/19 (100%) |
The reaction rates following AvP whole-cell DTP vaccination closely correlated with the rates observed with other commercially available whole-cell DTP vaccines.5 The incidence of adverse reactions was significantly lower following DT administration (p
As with any vaccine, vaccination with DT may not protect 100% of susceptible individuals.
TETANUS
Tetanus is an intoxication manifested primarily by neuromuscular dysfunction caused by a potent exotoxin elaborated by Clostridium tetani.
The occurrence of tetanus in the US has decreased dramatically from 560 reported cases in 1947 to a record low of 48 reported cases in 1987. Tetanus in the US is primarily a disease of older adults. Of 99 tetanus patients with complete information reported to the Centers for Disease Control and Prevention (CDC) during 1987 and 1988,68% were ≥50 years of age, while only six were
In 4% of tetanus cases reported during 1987 and 1988,no wound or other condition was implicated. Non-acute skin lesions, such as ulcers, or medical conditions such as abscesses, were reported in association with 14% of cases.2
Spores of C. tetani are ubiquitous. Serologic tests indicate that naturally acquired immunity to tetanus toxin does not occur in the US.2 Thus, universal primary vaccination, with subsequent maintenance of adequate antitoxin levels by means of appropriately timed boosters, is necessary to protect persons among all age-groups. Tetanus toxoid is a highly effective antigen, and a completed primary series generally induces protective levels of neutralizing antibodies to tetanus toxin that persist for ≥10 years.2
The potency of diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) toxoids was determined on the basis of immunogenicity studies with a comparison to a serological correlate of protection (0.01 antitoxin units/mL) established by the Panel on Review of Bacterial Vaccines & Toxoids.7
REFERENCES
2. Recommendations of the Advisory Committee on Immunization Practices (ACIP). Diphtheria, Tetanus, and Pertussis: Recommendations for vaccine use and other preventive measures. MMWR 40:No.RR-10,1991
3. Pichichero ME, et al. Pediatric diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) toxoids-adsorbed vaccine: Immune response to the first booster following the diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) toxoids vaccine primary series. Pediatr Infec Dis 5:428-430,1986
4. Barkin RM, et al. Pediatric diphtheria and tetanus (diphtheria and tetanus (diphtheria and tetanus toxoids) toxoids) toxoids (DT) vaccine: Clinical and immunologic response when administered as the primary series. J Pediatr 106:779-781,1985
5. Baraff L, et al. DTP associated reactions: An analysis by injection site, manufacturer, prior reactions and dose. Pediatr 73:31,1984
6. Centers for Disease Control and Prevention (CDC).Summary of Notifiable Diseases, United States 1992.MMWR 41:No.55,1993
7. Department of Health and Human Services, Food and Drug Administration. Biologicals Products; Bacterial Vaccines and Toxoids; Implementation of Efficacy Review; Proposed Rule. Federal Register Vol 50 No 240,pp 51002-51117,1985