What is the recommended post-exposure prophylaxis regimen for an individual exposed to a potential rabies source, specifically regarding the administration of anti-rabies vaccine (Intramuscular (IM) or Intradermal (ID) route)?

Rabies Post-Exposure Prophylaxis: Intramuscular Administration is Standard

For individuals exposed to potential rabies sources, administer a 4-dose intramuscular (IM) vaccine regimen on days 0,3,7, and 14, combined with human rabies immune globulin (HRIG) at 20 IU/kg on day 0 for previously unvaccinated persons. 1, 2

Immediate Wound Management

• Thoroughly wash all wounds with soap and water for 15 minutes immediately—this is the single most effective measure for preventing rabies infection. 2, 3
• Follow with irrigation using a virucidal agent such as povidone-iodine solution if available. 1, 2
• Avoid suturing wounds when possible, as closure may trap virus in tissue. 3

Standard Post-Exposure Prophylaxis Regimen (Previously Unvaccinated)

Vaccine Administration

• Administer 1.0 mL of human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV) intramuscularly on days 0,3,7, and 14. 1, 2
• Day 0 is defined as the day the first dose is given, not necessarily the day of exposure. 2
• Inject in the deltoid muscle for adults and older children, or the anterolateral thigh for young children. 1, 2, 4
• Never use the gluteal area—this produces inadequate antibody response and has been associated with vaccine failure. 2, 3, 5

Human Rabies Immune Globulin (HRIG)

• Administer exactly 20 IU/kg body weight on day 0, ideally simultaneously with the first vaccine dose. 1, 2, 5
• Infiltrate the full calculated dose around and into all wounds if anatomically feasible; administer any remaining volume intramuscularly at a site distant from vaccine administration. 1, 2, 5
• Never administer HRIG in the same syringe or at the same anatomical site as the vaccine. 1, 2, 5
• Do not exceed 20 IU/kg—higher doses suppress active antibody production. 1, 2, 3
• If HRIG was not given on day 0, it can still be administered up to and including day 7 after the first vaccine dose. 2, 3, 5

Special Populations

Immunocompromised Patients

• Administer a 5-dose vaccine regimen (days 0,3,7,14, and 28) plus HRIG at 20 IU/kg, even if previously vaccinated. 1, 2, 4
• This includes patients on corticosteroids, other immunosuppressive agents, or with conditions like HIV or chronic lymphoproliferative leukemia. 2
• Perform serologic testing 1-2 weeks after the final dose to confirm adequate antibody response. 2, 4

Previously Vaccinated Persons

• Administer only 2 doses of vaccine (on days 0 and 3) and do NOT give HRIG. 1, 2, 3
• This applies to anyone who completed a prior pre-exposure or post-exposure vaccination series with a cell culture vaccine. 1, 2
• HRIG will inhibit the anamnestic antibody response in previously vaccinated persons—never give it. 2, 3

Pediatric Patients

• Children receive the same vaccine dose volume (1.0 mL) and HRIG dose (20 IU/kg) as adults. 2, 4
• Use the anterolateral thigh for vaccine administration in young children. 1, 4, 5

Timing Considerations

• Initiate PEP as soon as possible after exposure, ideally within 24 hours. 2, 3
• However, there is no absolute cutoff—treatment remains indicated even if weeks or months have elapsed since exposure, as rabies is nearly 100% fatal once clinical symptoms develop. 2, 3
• Delays of a few days for individual doses are unimportant, though longer lapses require serologic assessment. 2

Intradermal (ID) Route: Not Standard in the United States

While research supports intradermal administration as safe and immunogenic—particularly the 1-week, 2-site ID schedule which reduces vaccine costs by 60-70%—the current U.S. guidelines recommend only intramuscular administration. 1, 2, 6, 7 The ID route is used primarily in resource-limited settings where vaccine cost is prohibitive. 6, 7 For standard practice in the United States, use the IM route as outlined above.

Critical Pitfalls to Avoid

• Never inject vaccine in the gluteal area—this is associated with vaccine failure. 2, 3, 5
• Never give HRIG to previously vaccinated persons. 2, 3
• Never administer HRIG and vaccine in the same syringe or anatomical site. 2, 3, 5
• Never exceed the 20 IU/kg dose of HRIG. 1, 2, 3
• Never upgrade immunocompetent patients to the 5-dose regimen unnecessarily, but never use the 4-dose schedule for immunocompromised patients. 1, 2