1. Clinical Overview
Rabies vaccine, Human (NA) is a sterile, freeze-dried suspension of inactivated rabies virus prepared from the Wistar Rabies PM/WI 38-1503-3M strain, propagated in human diploid cells (HDCV). It is a purified, inactivated, cell-culture derived vaccine used for pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) against rabies. It induces active immunity by stimulating the production of virus-neutralizing antibodies (VNA) against the rabies virus glycoprotein.
| Onset | Duration | Bioavailability |
|---|---|---|
| Antibody response typically begins within 7-10 days after the first dose of a primary series. Protective titers (≥0.5 IU/mL as per WHO/ACIP) are usually achieved by day 14 of a post-exposure regimen. | Duration of immunity varies. After a complete primary series (3 doses for PrEP), protective antibody levels can persist for several years. Booster doses are recommended based on continuous or frequent risk exposure or after a potential rabies exposure in previously vaccinated individuals. | Not applicable (N/A) for intramuscular/subcutaneous administration of a vaccine. Immunogenicity is the relevant measure. |
2. Mechanism of Action
The vaccine contains inactivated rabies virus. Upon intramuscular or intradermal administration, the viral antigens are taken up by antigen-presenting cells (APCs) and presented to helper T cells (CD4+). This activates B lymphocytes specific to the rabies virus glycoprotein (G protein), leading to clonal expansion and differentiation into plasma cells that produce virus-neutralizing antibodies (VNA). These antibodies bind to the virus, preventing its attachment and entry into host neurons, thereby neutralizing the infection. The process also generates memory B and T cells for a rapid anamnestic response upon future exposure.
3. Indications & Uses
- Post-exposure prophylaxis (PEP) against rabies following a Category II or III animal bite/scratch/lick on broken skin as per WHO/National Guidelines.
- Pre-exposure prophylaxis (PrEP) for individuals at high, continuous, or frequent risk of exposure to rabies virus (e.g., veterinarians, animal handlers, laboratory workers, travelers to endemic areas).
4. Dosage & Administration
Adult Dosage: Post-exposure (Previously Unvaccinated): 1.0 mL intramuscularly (IM) in the deltoid region on Days 0, 3, 7, 14, and 28 (Essen/5-dose IM regimen). The 4-dose IM regimen (Days 0, 3, 7, and 14) is also approved by WHO. Intradermal (ID) regimens (2-site or 8-site) require specific vaccine vials and trained personnel. Pre-exposure: 1.0 mL IM on Days 0, 7, and 21 or 28.
Administration: For IM use: Administer 1.0 mL into the deltoid muscle (anterolateral thigh in infants). NEVER administer in the gluteal region due to risk of reduced immunogenicity. For ID use: Administer 0.1 mL per site, using a specific intradermal technique (e.g., 2-site ID regimen on Days 0, 3, 7, and 28). The vaccine must be reconstituted strictly as per manufacturer's instructions using the supplied diluent. Use immediately after reconstitution.
5. Side Effects
Common side effects may include:
- Pain, tenderness, erythema, swelling, or itching at the injection site.
- Headache, dizziness.
- Malaise, fatigue.
- Myalgia, arthralgia.
- Low-grade fever.
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Chloroquine, Mefloquine (Antimalarials) | May attenuate antibody response when vaccine given intradermally; use IM route for PrEP if on these drugs. | Moderate |
| Immunosuppressants (Corticosteroids, Chemotherapy, Biologicals) | May reduce immunogenicity and vaccine efficacy. For PEP, administer vaccine regardless, but do not delay. Consider checking VNA titers. | Major |
| Other Vaccines | Can generally be administered concurrently at different sites. No significant interaction. | Minor |
| Rabies Immunoglobulin (RIG) | Concurrent administration is standard for Category III exposures. RIG does not suppress active immunity from the vaccine but must be given at a different anatomical site and never in the same syringe. | None (Synergistic) |
7. Patient Counselling
- DO complete the entire vaccination schedule as prescribed, even if the biting animal appears healthy later.
- DO immediately wash the wound with soap and running water for at least 15 minutes, followed by application of povidone-iodine or alcohol.
- DO inform the doctor about any past vaccinations or allergies.
- DO report to the clinic for each scheduled dose.
- DON'T apply irritants like chili powder, turmeric, or herbs to the wound.
- DON'T skip doses or delay vaccination.
- DON'T get the injection in the buttock.
8. Toxicology & Storage
Overdose: Unlikely due to fixed-dose vials. Theoretical overdose could exacerbate local and systemic side effects (severe pain, high fever, pronounced malaise).
Storage: Store un-reconstituted vials at +2°C to +8°C (refrigerator). DO NOT FREEZE. Protect from light. The diluent can be stored at room temperature. After reconstitution, use immediately (within 6-8 hours if stored at 2-8°C, but immediate use is best practice). Transport in a cold chain.