What is the recommended intramuscular (IM) dosage of rabies vaccine for a patient exposed to rabies?

Rabies Vaccine Intramuscular Dosage

For post-exposure prophylaxis in previously unvaccinated individuals, administer 1.0 mL of rabies vaccine intramuscularly on days 0,3,7, and 14, combined with human rabies immune globulin (HRIG) at 20 IU/kg on day 0. 1, 2

Post-Exposure Prophylaxis (PEP) for Previously Unvaccinated Persons

Standard 4-Dose Regimen:

• Vaccine dose: 1.0 mL per injection, administered intramuscularly 1, 2
• Schedule: Days 0,3,7, and 14 (day 0 is when the first dose is given, not necessarily the exposure date) 3, 1
• Injection site: Deltoid muscle for adults and older children; anterolateral thigh for young children 1, 2
• Critical: Never use the gluteal area—this produces inadequate antibody response and is associated with vaccine failure 1, 2

HRIG Administration:

• Dose: 20 IU/kg body weight, given once on day 0 1, 2
• Infiltrate the full calculated dose into and around the wound(s) if anatomically feasible; inject any remaining volume intramuscularly at a site distant from vaccine administration 1, 2
• Do not administer HRIG in the same syringe or at the same anatomical site as the vaccine 1, 2
• Do not exceed 20 IU/kg—higher doses suppress active antibody production 1, 2
• If HRIG was not given initially, it can still be administered up to and including day 7 after the first vaccine dose 1, 4

This updated 4-dose schedule replaced the older 5-dose regimen in 2010 based on strong evidence demonstrating equivalent efficacy with fewer doses. 3

Pre-Exposure Prophylaxis

For individuals at high risk (veterinarians, laboratory workers, travelers to endemic areas):

• Three 1.0 mL injections intramuscularly on days 0,7, and 21 or 28 3
• Administer in the deltoid area 3

Modified Regimens for Special Populations

Previously Vaccinated Persons:

• Only 2 doses required: 1.0 mL intramuscularly on days 0 and 3 3, 1, 2
• Do NOT give HRIG—it will inhibit the anamnestic antibody response 3, 1, 2

Immunocompromised Patients:

• 5-dose regimen: 1.0 mL intramuscularly on days 0,3,7,14, and 28 1, 2
• Plus HRIG at 20 IU/kg on day 0, even if previously vaccinated 1, 2
• Mandatory serologic testing 1-2 weeks after the final dose to confirm adequate antibody response 1

Pediatric Patients:

• Same vaccine dose volume (1.0 mL) and HRIG dose (20 IU/kg) as adults 1, 2
• Use anterolateral thigh for vaccine administration in young children 1, 2

Critical Timing and Wound Management

• Immediately wash all wounds thoroughly with soap and water for 15 minutes—this is the single most effective measure for preventing rabies 1, 2
• Follow with irrigation using a virucidal agent such as povidone-iodine solution if available 1, 2
• Initiate PEP as soon as possible after exposure, ideally within 24 hours, though treatment should begin immediately upon recognition of exposure even if weeks or months have elapsed 1, 2
• There is no absolute cutoff for initiating PEP—rabies is nearly 100% fatal once symptoms appear 1

Common Pitfalls to Avoid

• Never delay treatment while waiting for animal observation results in endemic areas—treatment can be discontinued if the animal remains healthy after 10 days 1
• Never give HRIG to previously vaccinated persons—this is a critical error that suppresses the memory immune response 1, 2
• Never use the gluteal area for vaccine administration—multiple vaccine failures have been documented with this route 1, 2
• Never exceed the 20 IU/kg dose of HRIG—higher amounts interfere with active antibody production 1, 2
• Delays of a few days for individual vaccine doses are acceptable and do not compromise protection, but every attempt should be made to adhere to the schedule 4