Diphtheria Toxoid
Definition And Pathophysiology
- Represents modified and purified toxin.
- Classified as inactivated vaccine.
- Requires multiple divided doses to decrease adverse effects and elicit high antibody titers.
- Demonstrates inability to eliminate Corynebacterium diphtheriae from skin or nasopharynx.
- Does not to provide permanent immunity.
- Waning immunity necessitates regular booster doses.
Immunogenicity And Protection
- Protective antibody titer defined as greater than 0.1 IU/mL.
- Primary immunization series induces satisfactory immune response in 95-100% of infants.
- Demonstrates 87% effectiveness against symptomatic disease.
- Shows 81% effectiveness in preventing severe disease.
- Confers 93% effectiveness against mortality.
Formulations And Antigen Content
- Standard pediatric vaccines (DTwP, DTaP, DT) contain 20-30 limit of flocculation (Lf) units.
- Standard dose DT shows more immunogenicity and less reactogenicity than conventional DTP.
- Reactogenicity increases significantly with advancing age.
- Reduced antigen formulations (Td, Tdap) contain smaller amounts (2 Lf units) of diphtheria toxoid.
- Reduced formulations exclusively utilized beyond 7 years of age.
- Available in multivalent combinations including Pentavalent and Hexavalent preparations.
Dosage, Route, And Storage
| Parameter | Recommendation |
|---|---|
| Volume | 0.5 mL. |
| Route | Intramuscular injection. |
| Site (Infants) | Anterolateral aspect of mid-thigh. |
| Site (Older Children/Adults) | Deltoid muscle. |
| Temperature | Maintain between 2-8°C. |
| Environmental Precautions | Protect from light and never freeze. |
Immunization Schedule
Primary Series And Pediatric Boosters
- Administer primary doses at 6, 10, and 14 weeks.
- Administer first booster at 15-18 months.
- Administer second booster at 4-6 years.
- Standard formulations contraindicated beyond 7 years of age.
Catch-Up Vaccination
- Under 7 years: Administer DTwP or DTaP at 0, 1, and 6 months.
- Above 7 years: Administer Tdap for first dose, followed by Td at 1 and 6 months.
Adolescent And Adult Schedule
- Administer Tdap or Td booster at 10-12 years.
- Provide decennial Td or Tdap boosters throughout life.
- Provide single Tdap or Td dose during each pregnancy, preferably between 27 and 36 weeks gestation.
Adverse Effects And Contraindications
Common Reactions
- Local pain, redness, and swelling frequently reported.
- Systemic reactions include fever, anorexia, fussiness, and vomiting.
- Administration of excessive toxoid doses leads to severe local immune complex-mediated Arthus reaction.
Contraindications
- Absolute contraindication includes severe allergic reaction or anaphylaxis to previous dose.
- Progressive neurological disease forms relative contraindication for pertussis-containing combinations, warranting DT utilization instead.