Rabies Post‑Exposure Prophylaxis (PEP) for Rat Bites

1. Risk Assessment and Decision‑Making

• In the United States and other developed nations, routine rabies PEP is not recommended after a rat bite because small rodents are virtually never infected with rabies and have not been documented to transmit the virus to humans. (Centers for Disease Control and Prevention) 1
• Healthcare providers should first consult local or state public‑health authorities before initiating rabies PEP for rodent bites, as the overall risk is typically negligible. (CDC) 1
• The decision to treat should consider local rabies epidemiology, the animal’s behavior (unprovoked vs. provoked attack), and any unusual circumstances that might suggest a higher rabies risk. (CDC) 1
• If the rat can be captured, observation or laboratory testing of the animal is preferred to automatic initiation of PEP. (CDC) 1

2. Immediate Wound Management

• Thoroughly wash the bite wound with soap and water for approximately 15 minutes immediately after the incident. (Clinical Practice Guidelines) [2][3]
• If available, irrigate the wound with a virucidal agent such as povidone‑iodine solution. (Clinical Practice Guidelines) [2][3]

3. Tetanus Prophylaxis

• Assess the patient’s tetanus immunization status and administer tetanus toxoid or tetanus immune globulin according to standard wound‑care protocols. (CDC) 1

4. Rabies Immune Globulin (HRIG) – Unvaccinated Individuals

• Give human rabies immune globulin (HRIG) at 20 IU per kilogram of body weight on day 0 (the same day as the first vaccine dose). (Clinical Practice Guidelines) [2][4]3
• Infiltrate the calculated HRIG dose directly into and around all bite wounds whenever anatomically feasible. (Clinical Practice Guidelines) [2][4]3
• Any remaining HRIG volume should be injected intramuscularly at a site distant from the vaccine injection. (Clinical Practice Guidelines) [2][4]3
• HRIG may be administered up to day 7 if missed on day 0, but must not be given after day 7. (Clinical Practice Guidelines) [2][3]
• Do not mix HRIG with the rabies vaccine in the same syringe or inject them at the same anatomical site. (Clinical Practice Guidelines) [2][4]3
• Do not exceed the 20 IU/kg dose, as excess HRIG can partially suppress the active antibody response. (Clinical Practice Guidelines) [2][4]3
• HRIG should not be given to individuals who have previously completed a full rabies vaccination series, because it may inhibit the anamnestic response. (Clinical Practice Guidelines) 3

5. Rabies Vaccine Schedule

5.1 Immunocompetent, Previously Unvaccinated Persons

• Administer 1.0 mL of inactivated rabies vaccine (HDCV or PCECV) intramuscularly on days 0, 3, 7, and 14 (four‑dose schedule). (Clinical Practice Guidelines) [2][3]
• The same 1.0 mL dose is used for all ages, including children and infants. (Clinical Practice Guidelines) [2][4]

5.2 Injection Sites

• Adults and older children: deltoid muscle (mandatory). (Clinical Practice Guidelines) [2][3]
• Infants and young children: anterolateral thigh. (Clinical Practice Guidelines) [2][4]
• Never use the gluteal region, as it yields significantly lower neutralizing antibody titers. (Clinical Practice Guidelines) [2][3]

5.3 Immunocompromised Individuals

• Use a five‑dose schedule: days 0, 3, 7, 14, and 28. (Clinical Practice Guidelines) [2][3]

5.4 Previously Vaccinated Individuals (Documented Complete Prior Series)

• Give only two vaccine doses on days 0 and 3, and do not administer HRIG. (Clinical Practice Guidelines) [2][3]

6. Timing and Continuity of Prophylaxis

• Start rabies PEP as soon as possible after exposure, regardless of the time elapsed since the bite. (Clinical Practice Guidelines) 3
• Minor delays of a few days for individual vaccine doses do not compromise overall efficacy. (Clinical Practice Guidelines) 2
• If a dose is missed, resume the series with the same intervals without restarting the entire schedule. (Clinical Practice Guidelines) 2
• Do not postpone treatment while awaiting animal‑testing results; begin PEP immediately and discontinue only if the animal later tests negative. (Clinical Practice Guidelines) 3

7. Common Pitfalls to Avoid

• Do not reduce the vaccine volume in children; they receive the full 1.0 mL dose. (Clinical Practice Guidelines) [2][4]
• Do not inject the vaccine into the gluteal region, as this markedly reduces immunogenicity. (Clinical Practice Guidelines) [2][3]
• Do not underdose HRIG by failing to infiltrate wounds completely; inadequate infiltration has been linked to rare prophylaxis failures. (Clinical Practice Guidelines) [4][3]
• Do not give HRIG after day 7, because the vaccine‑induced antibody response is presumed to have occurred by then. (Clinical Practice Guidelines) [2][3]
• Do not omit vaccine doses in immunocompromised patients; they must complete the five‑dose schedule. (Clinical Practice Guidelines) 2

Management of Missed Rabies Post‑Exposure Prophylaxis Doses in Immunocompromised Patients

Immediate Management of a Missed Dose

• Administer the missed day‑3 rabies vaccine dose immediately when the patient presents on day 7; this dose then counts as the second dose of the series despite a 4‑day delay. 5

Completion of the 5‑Dose Immunocompromised Schedule

• Immunocompromised patients must receive all five doses on days 0, 3, 7, 14, and 28; the schedule cannot be shortened. 6
• After giving the delayed second dose on day 7, schedule the third dose for day 14 (7 days after the dose just administered). 7
• Continue the series with the remaining doses on days 21 and 28 to achieve the full five‑dose regimen. 5
• The four‑dose regimen (days 0, 3, 7, 14) is reserved only for immunocompetent individuals and must not be applied to immunocompromised patients. 6
• Because immunosuppressed patients have impaired antibody responses, the fifth dose on day 28 is essential for adequate protection. 7

Human Rabies Immune Globulin (HRIG) Administration

• If HRIG was not given on day 0, it may still be administered up to and including day 7 of the PEP series. 5
• The recommended HRIG dose is 20 IU/kg body weight, with the full volume infiltrated into and around the wound(s) when anatomically feasible; any remaining volume should be given intramuscularly at a site distant from the vaccine injection. 6

Dose Count and Schedule Integrity

• Do not reduce the immunocompromised schedule to four doses, even when individual doses are delayed; adherence to the five‑dose schedule is mandatory. 7

Injection Site Recommendations

• For adults and older children, rabies vaccine must be administered intramuscularly in the deltoid muscle only. 5
• The gluteal region must be avoided because it yields significantly lower neutralizing antibody titers and has been linked to prophylaxis failures. 6

Immunologic Considerations and Serologic Testing

• Immunocompromised individuals generate weaker immune responses to rabies vaccine, justifying the extended five‑dose schedule. 7
• Routine antibody testing is not required for healthy patients, but immunocompromised patients may benefit from rabies‑virus neutralizing antibody titers measured 1–2 weeks after the final dose. 6
• A protective titer is defined as ≥ 0.5 IU/mL by the rapid fluorescent focus inhibition test (RFFIT). 7
• If post‑vaccination titers are below the protective threshold, additional booster doses should be considered in consultation with infectious‑disease specialists. 6