Should Tdap or Td be given for tetanus prophylaxis after a cat bite?

Tetanus Prophylaxis for Cat Bite Wounds

For tetanus prophylaxis after a cat bite, Tdap (tetanus, diphtheria, acellular pertussis) is preferred for persons aged ≥11 years who have not previously received Tdap or whose Tdap history is unknown; otherwise, Td should be used if a tetanus toxoid-containing vaccine is indicated. 1

Decision Algorithm for Tetanus Prophylaxis After Cat Bite

Step 1: Assess Vaccination History

• Complete vaccination history (≥3 doses) with last dose <5 years ago: No tetanus prophylaxis needed
• Complete vaccination history (≥3 doses) with last dose ≥5 years ago: Tetanus toxoid-containing vaccine indicated
• Unknown or incomplete vaccination history (<3 doses): Tetanus toxoid-containing vaccine AND Tetanus Immune Globulin (TIG) indicated

Step 2: Select Appropriate Vaccine

• Age <7 years: DTaP
• Age 7-10 years: Td
• Age ≥11 years:
  • If never received Tdap or Tdap history unknown: Tdap
  • If previously received Tdap: Td
  • If pregnant: Tdap regardless of previous Tdap history
  • If Td unavailable: Tdap may be administered

Step 3: Special Considerations

• Immunocompromised patients (including HIV): Should receive TIG regardless of vaccination history 1, 2
• Pregnant women: Should receive Tdap if tetanus prophylaxis is indicated 1, 2

Rationale for Recommendations

Cat bites are considered "dirty wounds" as they are contaminated with saliva and potentially soil or dirt 1. The Advisory Committee on Immunization Practices (ACIP) classifies animal bites under "all other wounds" category, which requires tetanus prophylaxis if ≥5 years have passed since the last tetanus toxoid-containing vaccine 1.

For adults who have completed the primary series but require a booster, Tdap is preferred over Td if they have not previously received Tdap. This recommendation serves dual purposes:

1. Providing tetanus protection
2. Boosting pertussis immunity, which is particularly important given increasing pertussis incidence in adolescents and adults 3, 4

Studies have shown that Tdap is as immunogenic as Td for tetanus and diphtheria protection, while also providing robust immune responses to pertussis antigens 5, 6. The safety profile of Tdap is similar to that of Td 6.

Important Clinical Considerations

• Wound care: Immediate and thorough cleaning is critical for tetanus prevention, with gentle irrigation using water or diluted iodopovidone solution 2
• TIG administration: When both TIG and tetanus toxoid-containing vaccine are indicated, administer using separate syringes at different anatomical sites 1, 7
• Documentation: Make a thorough attempt to determine whether the patient has completed the primary vaccination series; those with unknown histories should be considered to have had no previous tetanus toxoid-containing vaccine 1, 7
• Military service: Patients with military service since 1941 can be considered to have received at least one dose of tetanus toxoid, but completion of a primary series cannot be assumed 7

Pitfalls to Avoid

1. Underestimating the risk: Cat bites can lead to tetanus despite previous immunization 8
2. Delaying prophylaxis: Tetanus prophylaxis should be administered promptly as part of wound management
3. Incorrect vaccine selection: Using Td when Tdap is indicated in patients who have never received Tdap misses an opportunity to protect against pertussis
4. Overlooking TIG: Patients with unknown or incomplete vaccination histories require both tetanus toxoid-containing vaccine and TIG
5. Neglecting special populations: Immunocompromised patients require TIG regardless of vaccination history 1, 2

By following these evidence-based recommendations, clinicians can provide optimal tetanus prophylaxis after cat bites while simultaneously addressing pertussis protection when appropriate.