What is the indication for Rabies Immunoglobulin (RIG) in post-exposure prophylaxis?

Rabies Immunoglobulin (RIG) Indications

Rabies immunoglobulin is indicated for all previously unvaccinated individuals with Category III exposures (transdermal bites or scratches, mucous membrane contamination with saliva) from animals suspected or confirmed to be rabid, administered at 20 IU/kg body weight on day 0 of post-exposure prophylaxis. 1, 2

Primary Indications for RIG Administration

Previously Unvaccinated Persons

• RIG is required for all previously unvaccinated individuals receiving rabies post-exposure prophylaxis (PEP) who have sustained:

  • Any penetration of skin by teeth (bite exposure) from a rabid or suspected rabid animal 2
  • Scratches, abrasions, open wounds, or mucous membranes contaminated with saliva or potentially infectious material (brain tissue) from a rabid animal 2
  • Any physical contact with bats when bite or mucous membrane contact cannot be excluded, as bat bites may be undetectable 2

• The combination of RIG and vaccine is considered acceptable postexposure prophylaxis for preventing rabies, which is nearly 100% fatal once clinical symptoms develop 1, 2

Specific Animal Exposures Requiring RIG

• High-risk animals (skunk, bat, fox, coyote, raccoon, bobcat, other carnivores, woodchuck) should be regarded as rabid unless proven negative by laboratory testing, and exposures require both RIG and vaccine 2
• Dogs and cats that are rabid, suspected rabid, or unavailable for 10-day observation require RIG administration 2
• Livestock, rodents, and lagomorphs should be considered individually in consultation with local public health officials 2

Critical Timing Window for RIG Administration

• RIG should be administered ideally on day 0 (the day the first vaccine dose is given), simultaneously with the first rabies vaccine dose 1, 2
• RIG can be administered up to and including day 7 after the first vaccine dose if it was not given initially 1, 3, 2
• Beyond day 7, RIG is NOT indicated because an antibody response to cell culture vaccine is presumed to have occurred, and passive immunization becomes unnecessary and potentially counterproductive 3, 2

Populations Who Should NOT Receive RIG

Previously Vaccinated Individuals

• Previously vaccinated persons require only 2 doses of vaccine (days 0 and 3) and should NOT receive RIG, as it will inhibit the anamnestic antibody response 1, 2
• This applies to anyone who has completed a recommended pre-exposure or post-exposure vaccination series with a cell culture vaccine and has documented adequate rabies antibody titer 1, 2

Re-exposure Within 6 Months

• Individuals re-exposed within 6 months after completing PEP require only 2 vaccine doses without RIG, as they develop a rapid memory immune response 3

Dosing and Administration Requirements

• The dose is exactly 20 IU/kg body weight, calculated based on the patient's weight 1, 2
• The full calculated dose should be thoroughly infiltrated into and around all wound(s) if anatomically feasible 1, 2
• Any remaining volume after wound infiltration should be administered intramuscularly at a site distant from vaccine administration 1, 2
• Never exceed 20 IU/kg, as higher doses suppress active antibody production from the vaccine 1, 2

Special Populations

Immunocompromised Patients

• Immunocompromised individuals require RIG at 20 IU/kg on day 0 plus a 5-dose vaccine regimen (days 0,3,7,14,28), even if previously vaccinated 1, 4
• This includes patients on corticosteroids, other immunosuppressive agents, antimalarials, or those with HIV, chronic lymphoproliferative leukemia, or other immunosuppressive illnesses 1

Pediatric Patients

• Children receive the same dose of RIG (20 IU/kg) as adults, with no dose adjustment needed 1, 5
• The safety and efficacy of RIG in pediatric patients has been demonstrated, with 93.3% achieving adequate antibody levels 5

Critical Pitfalls to Avoid

• Never administer RIG in the same syringe or at the same anatomical site as the vaccine, as this may interfere with vaccine immunogenicity 1, 4, 2
• Never give RIG to previously vaccinated persons, as this is a critical error that suppresses the memory immune response 1, 4
• Never use the gluteal area for RIG injection due to risk of sciatic nerve injury 2
• Do not withhold RIG while waiting for animal observation results if the exposure occurred in a rabies-endemic area 1

Evidence Quality Note

Real-world adherence studies demonstrate high compliance with RIG patient selection (91%), dosing (98%), and timing (100%), though only 56% of eligible patients received proper wound infiltration as recommended 6. Clinical efficacy studies show 100% survival rates when RIG is administered as part of complete PEP, with mild adverse events occurring in only 11.4% of cases 7.