When should the rabies vaccine be administered after a bite or scratch from a potentially infected animal?

When to Give Rabies Vaccine After Animal Exposure

Rabies vaccine should be administered immediately (within 24 hours) after any bite or scratch from a potentially rabid animal, along with rabies immune globulin (RIG) for previously unvaccinated persons, regardless of delay in presentation. 1, 2

Immediate Actions Upon Exposure

Wound Management (First Priority)

• Thoroughly wash all bite wounds and scratches with soap and water for 15 minutes immediately 1, 3
• Apply a virucidal agent such as povidone-iodine solution after washing 1
• This local wound treatment alone significantly reduces rabies transmission risk 1

Risk Assessment Criteria

High-Risk Exposures Requiring Immediate Vaccination:

Animal Species:

• All bats - Any physical contact with bats when bite, scratch, or mucous membrane contact cannot be excluded requires immediate prophylaxis 2
• Wild carnivores (raccoons, skunks, foxes) - Initiate prophylaxis immediately unless the animal is available for rapid laboratory testing 2
• Dogs/cats in rabies-endemic areas (developing countries in Asia, Africa, Central/South America) - Start treatment immediately; can discontinue if animal remains healthy during 10-day observation 1
• Stray or unwanted dogs/cats - Euthanize immediately and test; begin prophylaxis pending results 1

Low-Risk Exposures (Consult Health Department):

• Small rodents (squirrels, rats, mice, hamsters, guinea pigs) and lagomorphs (rabbits, hares) rarely transmit rabies 2

Vaccination Protocols

For Previously Unvaccinated Persons

Standard Post-Exposure Prophylaxis (PEP) Regimen:

• Rabies Immune Globulin (RIG): 20 IU/kg body weight given once on day 0 - infiltrate full dose into and around all wounds if anatomically feasible; inject remainder intramuscularly at site distant from vaccine 1, 2
• If RIG not given on day 0, it can still be administered through day 7 of the vaccine series 1, 2
• Beyond day 7, do NOT give RIG as antibody response to vaccine is presumed to have occurred 1

Vaccine Schedule (Current ACIP Recommendation):

• 4-dose regimen: Days 0,3,7, and 14 4
• Alternative 5-dose regimen: Days 0,3,7,14, and 28 (older protocol, still acceptable) 1
• Administer intramuscularly in the deltoid muscle for adults and older children 1, 5
• For infants and young children, use anterolateral thigh 1, 5
• NEVER inject in gluteal area - subcutaneous fat interferes with immune response and has been associated with vaccine failure 5

For Previously Vaccinated Persons

Definition: Persons with documented rabies virus neutralizing antibody titer who completed a recommended pre-exposure or post-exposure regimen with cell culture vaccine 2

Simplified Protocol:

• Give vaccine ONLY (no RIG) 1, 2
• 2-dose schedule: Days 0 and 3 1

Critical Timing Considerations

No Time Limit for Starting Prophylaxis:

• Begin treatment regardless of interval between exposure and presentation, even if months have passed 1, 2
• Incubation periods exceeding 1 year have been documented in humans 1
• Once clinical symptoms appear, rabies is virtually 100% fatal 3

Observation Period for Healthy Domestic Animals:

• Healthy dogs, cats, or ferrets that bite should be confined and observed for 10 days 1
• Do NOT vaccinate the animal during observation period to avoid confusing rabies signs with vaccine side effects 1
• If animal remains healthy for 10 days, discontinue human prophylaxis 1
• If animal develops illness, euthanize immediately and test brain tissue; continue human prophylaxis 1

Common Pitfalls to Avoid

Critical Errors:

• Never delay treatment waiting for animal test results - begin immediately for high-risk exposures 2
• Never administer RIG in same syringe or anatomical site as vaccine - can suppress active antibody production 1
• Never exceed recommended RIG dose (20 IU/kg) - excess can partially suppress active antibody production 1
• Never assume prior vaccination provides lifelong protection - antibody levels decline over time, and re-exposure requires assessment 6

Special Circumstances:

• Unprovoked attacks are more likely to indicate rabid animal than provoked attacks 1, 2
• Category III exposures (transdermal bites, scratches, or mucous membrane contamination with saliva) require both RIG and vaccine 3, 7
• Immunosuppressed patients should follow the 5-dose vaccine schedule regardless of newer 4-dose recommendations 4

Human diploid cell vaccine (HDCV) induces excellent antibody response with geometric mean titers of 12.9 IU/mL at day 49, well above the WHO-specified protective titer of 0.5 IU/mL 5. The 4-dose regimen recommended since 2009 is safe, effective, and cost-saving compared to the older 5-dose schedule 4.