What is the recommended post-exposure prophylaxis (PEP) for a patient exposed to a potential rabies source, such as an animal bite, considering their health status, age, and potential allergies or immunodeficiencies?

Rabies Post-Exposure Prophylaxis (PEP)

Immediate Action for Previously Unvaccinated Persons

For any patient exposed to a potential rabies source through a bite or nonbite exposure (scratches, open wounds, or mucous membranes contaminated with saliva), immediately initiate a 4-dose rabies vaccine regimen (days 0,3,7, and 14) combined with rabies immune globulin (RIG) at 20 IU/kg on day 0, along with thorough wound washing—this protocol is nearly 100% effective when administered promptly. 1, 2

Critical First Step: Wound Management

• Immediately wash all wounds with soap and water for 15 minutes before any other intervention—this single measure is perhaps the most effective step for preventing rabies infection and has been shown in animal studies to markedly reduce transmission likelihood 3, 1, 2
• Follow with irrigation using a virucidal agent such as povidone-iodine solution if available 3, 1
• Administer tetanus prophylaxis and antibiotics as indicated 3, 4
• Avoid suturing wounds when possible unless cosmetically necessary or to prevent bacterial infection 4

Standard PEP Regimen Components

Rabies Vaccine Schedule

• Administer 4 doses of HDCV or PCECV at 1.0 mL intramuscularly on days 0,3,7, and 14 (day 0 is when the first dose is given, not necessarily the exposure date) 3, 1, 2
• Inject in the deltoid muscle for adults and older children; use the anterolateral thigh for young children 3, 1, 2
• Never use the gluteal area—this produces inadequate antibody response and has been associated with vaccine failures 3, 1, 2

Rabies Immune Globulin (RIG) Administration

• Administer RIG at 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; inject any remaining volume intramuscularly at a site distant from vaccine administration 3, 1, 2
• Do not administer RIG 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
• RIG can be administered up to and including day 7 after the first vaccine dose if not given initially 3, 2, 5

Modified Regimens for Special Populations

Previously Vaccinated Persons

• Administer only 2 doses of vaccine on days 0 and 3—no RIG is needed 3, 1, 2
• This applies to anyone who completed a recommended pre-exposure or post-exposure vaccination regimen with a cell culture vaccine 3, 2
• Do not give RIG to previously vaccinated persons—it will inhibit the anamnestic antibody response 3, 1

Immunocompromised Patients

• Use a 5-dose vaccine regimen (days 0,3,7,14, and 28) plus RIG at 20 IU/kg, even if previously vaccinated 1, 2, 4
• This includes patients on corticosteroids, other immunosuppressive agents, antimalarials, or with immunosuppressive illnesses (HIV, chronic lymphoproliferative leukemia) 1
• Obtain serologic testing 7-14 days after the final dose to confirm adequate antibody response (≥0.5 IU/mL or complete virus neutralization at 1:5 dilution by RFFIT) 1, 2
• If no adequate response is detected, consult with public health officials 1

Pediatric Patients

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

Timing Considerations

• Initiate PEP as soon as possible after exposure, ideally within 24 hours—delays of even hours matter significantly because rabies is nearly 100% fatal once clinical symptoms develop 3, 1, 2
• There is no absolute cutoff for initiating PEP—treatment should begin immediately upon recognition of exposure, even if weeks or months have elapsed, as incubation periods can exceed one year 3, 1, 2
• Delays of a few days for individual vaccine doses are unimportant and do not compromise protection 2

Exposure Risk Assessment Algorithm

Bite Exposures

• Any penetration of skin by teeth constitutes a bite exposure requiring evaluation 3
• All bites, regardless of location, represent potential rabies transmission risk 3
• Bat bites can inflict minor injury and be undetected, requiring special assessment 3

Nonbite Exposures

• Scratches, abrasions, open wounds, or mucous membranes contaminated with saliva or neural tissue from a rabid animal constitute nonbite exposures requiring PEP 3, 5
• If the material containing virus is dry, it is considered noninfectious—no prophylaxis needed 3, 5
• Petting a rabid animal or contact with blood, urine, or feces alone does not constitute exposure 3, 5

Animal-Specific Considerations

High-Risk Animals (Immediate PEP)

• Bats, skunks, raccoons, foxes, coyotes, bobcats: Regard as rabid unless proven negative by laboratory testing—initiate PEP immediately 3, 5
• Stray or unwanted dogs/cats: Euthanize immediately and test, or initiate PEP 3, 5

Domestic Dogs, Cats, Ferrets

• Healthy and available for observation: Confine and observe for 10 days; begin PEP at first sign of rabies in the animal 3, 5
• Rabid or suspected rabid: Initiate PEP immediately 5
• Unknown/escaped: Consult public health officials; in rabies-endemic areas, strongly consider initiating PEP 3, 5

Low-Risk Animals

• Small rodents (squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats, mice) and lagomorphs (rabbits, hares): Rarely require PEP—consult local health department 3, 5
• Exception: Woodchucks in raccoon rabies-endemic areas accounted for 93% of rodent rabies cases 3

Critical Pitfalls to Avoid

1. Never administer vaccine in the gluteal area—this is associated with vaccine failure 3, 1, 2
2. Never give RIG to previously vaccinated persons—it suppresses the memory immune response 3, 1
3. Never exceed 20 IU/kg of RIG—higher doses inhibit active antibody production 1, 2
4. Do not withhold PEP while waiting for animal observation results in high-risk situations—treatment can be discontinued if the animal remains healthy after 10 days 2
5. Do not delay wound washing—it is the most crucial first step 1, 2, 4
6. For immunocompromised patients, do not use the standard 4-dose regimen—upgrade to 5 doses with mandatory serologic testing 1, 2

Efficacy and Safety

• When administered promptly and appropriately, PEP is nearly 100% effective in preventing human rabies 3, 1, 2
• The 4-dose vaccine schedule is safe and effective, inducing adequate, long-lasting antibody response when used with timely wound care and RIG 6
• Over 1,000 persons annually in the United States receive incomplete regimens (3-4 doses) with no documented cases of rabies developing, even when >30% had confirmed exposure to rabid animals 2
• No case of human rabies in the United States has ever been attributed to receiving fewer than the complete vaccine course 2