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CLINICAL PHARMACOLOGY

Tetanus

Tetanus is an acute and often fatal disease caused by an extremely potent neurotoxin produced by C tetani. Protection against disease is due to the development of neutralizing antibodies to tetanus toxin. A serum tetanus antitoxin level of 0.01 IU/mL, measured by neutralization assays, is considered the minimum protective level.6,7 A tetanus antitoxoid level ≥ 0.1 IU/mL as measured by the enzyme-linked immunosorbent assay (ELISA) used in the booster immunization study of DECAVAC vaccine is considered protective [see Clinical Studies].

Diphtheria

Diphtheria is an acute toxin-mediated disease caused by toxigenic strains of C diphtheriae. Protection against disease is due to the development of neutralizing antibodies to diphtheria toxin. A serum diphtheria antitoxin level of 0.01 IU/mL is the lowest level giving some degree of protection.7,8 A diphtheria antitoxin level of 0.1 IU/mL is generally regarded as protective.8 Diphtheria antitoxin levels of ≥ 1.0 IU/mL have been associated with long-term protection.8 Antibodies to diphtheria toxin were measured by a microneutralization assay in the booster immunization study of DECAVAC vaccine [see Clinical Studies].

Clinical Studies

Primary Immunization

The effectiveness of primary immunization with tetanus toxoid and diphtheria toxoid used in DECAVAC vaccine was determined on the basis of an immunogenicity study, 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 A clinical study to evaluate the serological responses was performed in 58 individuals 6-58 years of age. Of these, 46 persons had no evidence of prior immunity to tetanus toxin and 47 persons had no evidence of prior immunity to diphtheria toxin. The results indicated protective levels of antibody were achieved in greater than 90% of the study population after primary immunization with both components.4

Booster Immunization

In a clinical study, the immune response to booster immunization with DECAVAC vaccine was evaluated in 516 adolescents 11-17 years of age and 509 adults 18-64 years of age. Participants had not received a tetanus or diphtheria toxoid-containing vaccine within the previous 5 years. Sera were obtained before and approximately 35 days after vaccination. Antibodies to tetanus toxoid were measured by an ELISA. Antibodies to diphtheria toxin were measured by a microneutralization assay. Seroprotection rates and booster response rates for tetanus are provided in Table 4. Seroprotection rates and booster response rates for diphtheria are provided in Table 5.

Table 4: Pre-vaccination and Post-vaccination Tetanus Seroprotection Rates and Booster Response Rates Following a Booster Dose of DECAVAC Vaccine in Adolescents and Adults 11 Through 64 Years of Age

Age Group (years) Na Tetanus Antitoxoid (IU/mL)
Pre-Vaccination 1 Month Post-Vaccination
% ≥ 0.1b (95% CI) % ≥ 1.0c (95% CI) % ≥ 0.1b (95% CI) % ≥ 1.0c (95% CI) % Boosterd (95% CI)
11-17 516 99.2 (98.0, 99.8) 43.8 (39.5, 48.2) 100.0 (99.3, 100.0) 99.4 (98.3, 99.9) 91.3 (88.5, 93.6)
18-64 509 95.9 (93.8, 97.4) 70.3 (66.2, 74.3) 99.8 (98.9, 100.0) 98.2 (96.7, 99.2) 66.8 (62.5, 70.9)
aN = number of participants in the per-protocol population with available data.
bWith the ELISA used in this study, a tetanus antitoxoid level of 0.1 IU/mL is considered the protective level.
cWith the ELISA used in this study, a tetanus antitoxoid level of 1.0 IU/mL is 10 times the protective level.
dBooster response is defined as: A four-fold rise in antibody concentration, if the pre-vaccination concentration was equal to or below the cut-off value and a two-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value. The cut-off value for tetanus was 2.7 IU/mL.

Table 5: Pre-vaccination and Post-vaccination Diphtheria Seroprotection Rates and Booster Response Rates Following a Booster Dose of DECAVAC Vaccine in Adolescents and Adults 11 Through 64 Years of Age

Age Group (years) Na Diphtheria Antitoxin (IU/mL)
Pre-Vaccination 1 Month Post-Vaccination
% ≥ 0.1b (95% CI) % ≥ 1.0c (95% CI) % ≥ 0.1b (95% CI) % ≥ 1.0c (95% CI) % Boosterd (95% CI)
11-17 515-516 70.7 (66.5, 74.6) 17.3 (14.1, 20.8) 99.8 (98.9, 100.0) 98.4 (97.0, 99.3) 95.0 (92.7, 96.7)
18-64 506-507 63.3 (59.0, 67.5) 16.0 (12.9, 19.5) 95.1 (92.8, 96.8) 79.9 (76.1, 83.3) 83.4 (79.9, 86.5)
aN = number of participants in the per-protocol population with available data.
bWith the microneutralization assay used in this study, a diphtheria antitoxin level of 0.1 IU/mL is generally regarded as protective.
cWith the microneutralization assay used in this study, diphtheria antitoxin levels ≥ 1.0 IU/mL have been associated with long term protection.

dBooster response is defined as: A four-fold rise in antibody concentration, if the pre-vaccination concentration was equal to or below the cut-off value and a two-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value. The cut-off value for diphtheria was 2.56 IU/mL.

REFERENCES

4 Myers MG, et al. Primary immunization with tetanus and diphtheria toxoids. JAMA 248:1982;2478-2480.

6 Wassilak SGF, et al. Tetanus toxoid. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. 5th ed. Philadelphia, PA: WB Saunders Company;2008:805-839.

7 Department of Health and Human Services, Food and Drug Administration. Biological Products; Bacterial Vaccines and Toxoids; Implementation of Efficacy Review; Proposed Rule. Federal Register Vol 50 No 240:1985; 51002-51117.

8 Vitek CR and Wharton M. Diphtheria toxoid. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. 5th ed. Philadelphia, PA: WB Saunders Company;2008:139-156.

Last reviewed on RxList: 9/29/2014
This monograph has been modified to include the generic and brand name in many instances.

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