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# Antirabies Vaccine
## Overview
Rabies vaccine is an inactivated virus preparation (either Human Diploid Cell Vaccine [HDCV] or Purified Chick Embryo Cell Vaccine [PCECV]) used for pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP). It induces active immunity to the rabies virus.
## Primary Indications
* **Pre-exposure prophylaxis (PrEP):** Indicated for individuals at high risk of exposure (e.g., veterinarians, laboratory workers, cave explorers).
* **Post-exposure prophylaxis (PEP):** Indicated for individuals bitten, scratched, or exposed to mucous membranes by a suspected rabid animal. Must be administered in combination with Rabies Immune Globulin (RIG) for severe exposures in unvaccinated individuals.
## Adult Dosing
* **PrEP:** 1 mL IM (deltoid) on days 0 and 7.
* **PEP (previously unvaccinated):** 1 mL IM on days 0, 3, 7, and 14.
* **PEP (previously vaccinated):** 1 mL IM on days 0 and 3 (RIG is not indicated).
* *Note:* Always follow local public health/CDC guidelines as protocols can change based on regional rabies prevalence and recent exposure history.
## Pediatric Dosing
* **Dosing:** Same as adults (1 mL IM).
* **Administration Site:** Children <2 years should receive injections in the anterolateral thigh. Children ≥2 years may receive injections in the deltoid muscle. **Never inject into the gluteal region** as it may result in lower antibody titers due to adipose tissue storage.
## Dose Adjustments
* **Standardization:** No dose adjustment based on weight is required; the full 1 mL dose is standard for all ages.
* **Immunocompromised:** Patients with immunosuppression should receive a full 4-dose series for PEP, and serologic testing 1–2 weeks after completion is recommended to confirm seroconversion.
## Contraindications
* **Hypersensitivity:** Severe allergic reaction (e.g., anaphylaxis) to a previous dose or vaccine component.
* **Pre-exposure:** If the patient is immunocompromised, the risk/benefit must be carefully weighed; titers should be monitored.
* *Note:* There are no absolute contraindications for PEP, as rabies is universally fatal; manage hypersensitivity reactions supportively.
## Adverse Effects
* **Common:** Pain, erythema, swelling, or induration at the injection site (up to 30-74%).
* **Systemic:** Headache, nausea, abdominal pain, muscle aches, and dizziness.
* **Rare:** Serum sickness-like reactions (may occur 2–21 days post-vaccination).
## Key Drug Interactions
* **Immunosuppressants/Corticosteroids:** These may diminish the immune response to the vaccine. Avoid administration during the vaccine series if possible. If unavoidable, verify seroconversion via titer testing.
## Monitoring
* **Efficacy:** Testing for rabies antibody titers is only recommended for individuals at continuous high risk of occupational exposure (e.g., lab workers handling live virus).
* **Safety:** Monitor for signs of serum sickness-like reactions following booster doses.
## Clinical Pearls
* **RIG Administration:** In PEP, Rabies Immune Globulin (RIG) should be infiltrated into and around the wound (as much as anatomically feasible) at the time of the first vaccine dose.
* **Route:** Always administer IM. Subcutaneous and intradermal injections are not recommended in the US as they may result in inadequate immune response.
* **Consultation:** Always coordinate with the local Health Department or the CDC Rabies Program for complex exposure cases.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practices vary by jurisdiction and institutional protocol. Always verify current prescribing information, CDC/WHO guidelines, and local health department requirements before administering vaccines.
