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# Antirabies Vaccine
## Overview
Rabies vaccine is an inactivated virus preparation used for pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP). Common formulations include Human Diploid Cell Vaccine (HDCV) and Purified Chick Embryo Cell Vaccine (PCECV).
## Primary Indications
* **Pre-exposure prophylaxis:** High-risk groups (e.g., veterinarians, laboratory workers, cave explorers, travelers to endemic areas).
* **Post-exposure prophylaxis (PEP):** Management of suspected rabies exposure (animal bite or scratch). Must be administered in combination with Rabies Immune Globulin (RIG) for non-immunized individuals.
## Adult Dosing
* **Pre-exposure (IM):** 1 mL IM in the deltoid on days 0 and 7. Follow-up booster doses depend on ongoing risk and serological titer monitoring.
* **Post-exposure (IM):** 1 mL IM in the deltoid on days 0, 3, 7, and 14.
* *Note:* Immunocompromised persons should receive a 5th dose on day 28.
* *Note:* If previously vaccinated, 1 mL IM on days 0 and 3 (no RIG required).
## Pediatric Dosing
* **Dosage:** Same as adults (1 mL IM).
* **Administration Site:** Children < 1 year: anterolateral thigh. Children ≥ 1 year: deltoid muscle.
* **Dosing Schedule:** Identical to adult schedule for both PrEP and PEP.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No dose adjustments necessary.
* **Immunocompromised:** Must receive the 5-dose series for PEP (days 0, 3, 7, 14, and 28). Serology testing 1–2 weeks after the series is recommended to ensure seroconversion.
## Contraindications
* **Severe hypersensitivity:** Prior anaphylactic reaction to the vaccine or any component (e.g., neomycin, polymyxin B, streptomycin).
* **Pre-exposure:** Generally withheld in patients with acute febrile illness; however, PEP is life-saving and should not be delayed by contraindications.
## Adverse Effects
* **Common:** Injection site pain, erythema, swelling, pruritus (<50%). Systemic reactions include headache, nausea, abdominal pain, myalgia, and dizziness.
* **Rare:** Serum sickness-like reactions (type III hypersensitivity) may occur 2–21 days post-vaccination, particularly with boosters.
## Key Drug Interactions
* **Corticosteroids/Immunosuppressants:** May interfere with the immune response to the vaccine; serologic monitoring is advised.
* **Rabies Immune Globulin (RIG):** Must be infiltrated at the wound site (if possible) and administered at a different anatomical site from the vaccine to avoid neutralization.
## Monitoring
* **Post-Exposure:** Monitor the wound site for signs of infection.
* **Immunocompromised:** Post-vaccination titer testing is essential to confirm seroconversion.
* **Clinical:** Observe for signs of serum sickness-like reactions (urticaria, arthralgia) in the weeks following administration.
## Clinical Pearls
* **Local Variability:** Post-exposure protocols regarding the number of doses and the necessity of RIG can vary by local health department guidelines and the specific animal species involved (e.g., bat vs. dog). Always verify with local public health authorities or CDC guidelines.
* **RIG Administration:** If RIG is indicated, it should be infiltrated into and around the wound; any remaining dose should be administered IM at a site distant from the vaccine.
* **Pregnancy/Lactation:** Rabies is fatal; pregnancy is never a contraindication to PEP.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult the latest CDC/WHO guidelines and the manufacturer’s product insert before prescribing or administering rabies vaccine, as protocols are situation-specific and subject to change.
