When is rabies immunoglobulin (RIG) indicated?

Indications for Rabies Immunoglobulin (RIG)

Rabies Immune Globulin (RIG) is indicated for previously unvaccinated individuals with potential rabies exposures, particularly those with Category III exposures (bites, scratches, or mucous membrane contamination with saliva from a suspected rabid animal), and should be administered as part of post-exposure prophylaxis along with rabies vaccine. 1, 2

Primary Indications for RIG

• Required for previously unvaccinated persons with rabies exposures 3, 1
• Not indicated for previously vaccinated individuals who have received complete pre-exposure or post-exposure prophylaxis with cell culture vaccines or have documented adequate rabies antibody titers 1, 2
• Must be administered with the first dose of vaccine (day 0) or can be given through the seventh day after the first vaccine dose 3, 2
• Beyond the seventh day, RIG is not indicated as an antibody response to the vaccine is presumed to have occurred 3, 2

Types of Exposures Requiring RIG

Category III Exposures (Highest Risk)

• Single or multiple transdermal bites or scratches
• Contamination of mucous membranes or broken skin with saliva
• Direct contact with bats 2

Animal Considerations

• Exposures from wild carnivores (skunks, bats, foxes, coyotes, raccoons, bobcats) should be considered high-risk 2
• Domestic animals (dogs, cats) that are:
  • Rabid or suspected rabid
  • Unknown or escaped and cannot be observed for 10 days 2

Proper Administration of RIG

• Dosage: 20 IU/kg body weight 1, 2
• Primary administration method: Local wound infiltration
  • The full dose should be infiltrated into and around all wounds if anatomically feasible 1, 2
  • Any remaining volume should be administered intramuscularly at a site distant from vaccine administration 1
• Recent evidence emphasizes that local wound infiltration is the primary mechanism of protection 4

Important Caveats and Pitfalls

1. Do not exceed recommended dosage as RIG can partially suppress active antibody production 3

2. Do not administer RIG to previously vaccinated individuals as it may inhibit the strength or rapidity of the expected immune response 1

3. Timing considerations:

   • Should be given immediately with the first vaccine dose
   • Can be given up to 7 days after first vaccine dose
   • Not indicated beyond 7 days 3, 2

4. Common administration errors:

   • Failure to infiltrate wounds (only 56% of eligible patients receive proper wound infiltration) 5
   • Incorrect dosing
   • Inappropriate patient selection 5

5. For multiple or extensive wounds, especially in small children, RIG may need to be diluted with saline to provide adequate volume for infiltration of all wounds 6

6. Suppression effect on vaccine response:

   • RIG can suppress vaccine immunogenicity
   • This effect is more pronounced with human RIG than equine RIG 7
   • This is why no more than the recommended dose should be administered 3

Special Situations

• When RIG is not immediately available: Initiate vaccine series immediately and administer RIG as soon as it becomes available (within 7 days of first vaccine dose) 6

• For immunocompromised patients: Standard RIG administration is recommended, but these patients may require special management including consultation with public health officials 1

• Pregnancy: Not a contraindication to RIG administration 1