When is Tdap (tetanus, diphtheria, and pertussis) vaccine recommended for a cat scratch?

Tetanus Prophylaxis for Cat Scratches

Tdap vaccine is indicated for cat scratches if more than 5 years have passed since the last tetanus toxoid-containing vaccine, as cat scratches are considered "dirty wounds" that require tetanus prophylaxis. 1

Wound Classification and Tetanus Risk

Cat scratches are classified as "dirty wounds" because they are contaminated with saliva and potentially soil or dirt. This classification affects tetanus prophylaxis recommendations:

• For clean, minor wounds: Tetanus toxoid-containing vaccine if >10 years since last dose
• For dirty wounds (including cat scratches): Tetanus toxoid-containing vaccine if >5 years since last dose 2, 1

Recommended Approach for Cat Scratch Management

Step 1: Assess Tetanus Vaccination History

• Determine when the patient last received a tetanus toxoid-containing vaccine
• If vaccination history is unknown or uncertain, consider the patient to have had no previous tetanus toxoid-containing vaccine 2

Step 2: Provide Appropriate Tetanus Prophylaxis

Based on vaccination history and wound type:

1. For patients with complete primary vaccination series:

   • If last dose was <5 years ago: No tetanus prophylaxis needed
   • If last dose was ≥5 years ago: Administer tetanus toxoid-containing vaccine 1

2. For patients with incomplete or unknown vaccination history:

   • Administer tetanus toxoid-containing vaccine
   • Consider Tetanus Immune Globulin (TIG) 250 units intramuscularly 2, 1

Step 3: Select Appropriate Vaccine Type

The choice of tetanus toxoid-containing vaccine depends on age and previous vaccination:

• Children <7 years: DTaP
• Children 7-10 years: Td
• Persons ≥11 years:
  • If never received Tdap or Tdap history unknown: Tdap preferred
  • If previously received Tdap: Td recommended 2, 1
• Pregnant women: Tdap preferred regardless of prior Tdap history 1

Special Considerations

Immunocompromised Patients

• Patients with immunocompromising conditions (including HIV) should receive TIG regardless of vaccination history 1

History of Adverse Reactions

• For individuals with history of Arthus reaction to previous tetanus or diphtheria toxoid-containing vaccine, defer vaccination for at least 10 years 2, 1
• For those with history of Guillain-Barré syndrome within 6 weeks of previous tetanus vaccination, carefully evaluate risks and benefits 1

Wound Care

• Immediate and thorough wound cleaning is critical for tetanus prevention
• Gently irrigate with water or diluted iodopovidone solution 1

Clinical Caution

Despite appropriate immunization, rare cases of tetanus after cat scratches have been reported. A case study documented mild generalized tetanus in a previously immunized 21-year-old female following cat scratches and bites, despite having received six vaccine shots during childhood and a booster dose five years earlier 3. This highlights that:

1. Tetanus remains possible even in previously immunized patients
2. Severity of disease is typically modulated by previous vaccination
3. Proper wound care remains essential even for vaccinated individuals

Remember that the case-fatality rate for tetanus remains high at approximately 25%, with higher rates in older adults, emphasizing the importance of appropriate prophylaxis 1.