1. Clinical Overview
Rabies Vaccine, Human (2.5IU) is a sterile, freeze-dried preparation of inactivated rabies virus (Pitman-Moore or Vero cell line) used for pre-exposure and post-exposure prophylaxis against rabies. It is a purified, potent, and highly immunogenic vaccine that induces active immunity by stimulating the production of virus-neutralizing antibodies (VNA). It is a critical component of rabies prevention in India, where rabies is endemic and a major public health concern.
| Onset | Duration | Bioavailability |
|---|---|---|
| Virus-neutralizing antibodies (VNA) typically appear within 7-14 days after the first dose, with protective titers (≥0.5 IU/mL) achieved in most individuals by day 14. | Immunity duration varies. After a complete primary series (pre- or post-exposure), memory B-cells provide long-term immunity. Booster doses are recommended for ongoing risk or after potential re-exposure. Protective antibody levels can persist for several years. | Not applicable (N/A) for injectable vaccines. Immunogenicity is the relevant measure, with seroconversion rates >99% after a complete post-exposure prophylaxis (PEP) regimen in immunocompetent individuals. |
2. Mechanism of Action
The vaccine contains inactivated rabies virus antigen. Upon administration, it is recognized by the host's immune system as foreign. Antigen-presenting cells (APCs) phagocytose the antigen, process it, and present viral peptides on MHC class II molecules to CD4+ T-helper cells. This activates B-lymphocytes specific to rabies virus glycoprotein (G protein) and nucleoprotein (N protein). Activated B-cells proliferate and differentiate into plasma cells that secrete rabies virus-neutralizing antibodies (VNA), primarily against the G protein. These antibodies bind to the virus, preventing its attachment and entry into host neurons, thereby neutralizing the infection.
3. Indications & Uses
- Post-Exposure Prophylaxis (PEP) against rabies following animal bites (dogs, cats, bats, monkeys, etc.)
- Pre-Exposure Prophylaxis (PrEP) for individuals at high risk of exposure (veterinarians, animal handlers, laboratory workers, travelers to endemic areas, children in high-risk areas)
4. Dosage & Administration
Adult Dosage: Post-Exposure (IM - Essen Regimen): 2.5IU, 1 mL intramuscularly in deltoid on Days 0, 3, 7, 14, and 28. Post-Exposure (ID - Updated Thai Red Cross Regimen): 0.1 mL intradermally at two sites on Days 0, 3, 7, and 28. Pre-Exposure (IM): 2.5IU, 1 mL IM on Days 0, 7, and 21 or 28.
Administration: For IM: Use deltoid (adults/children) or anterolateral thigh (infants). Do NOT administer in gluteal region. For ID: Administer over deltoid, ensuring a correct bleb (0.1 mL) is formed. Use a tuberculin syringe. Shake vial well before use. Reconstitute with supplied sterile water for injection. Use immediately after reconstitution.
5. Side Effects
Common side effects may include:
- Pain, erythema, swelling, and itching at injection site
- Low-grade fever, malaise, headache
- Myalgia, arthralgia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Immunosuppressants (Corticosteroids, Chemotherapy, Azathioprine, Cyclosporine, TNF-alpha inhibitors) | May diminish the immunological response to the vaccine, potentially leading to vaccine failure. PEP may require additional doses and serology. | Major |
| Chloroquine, other antimalarials | May interfere with antibody response if given concurrently with ID vaccination. Use IM route for PrEP if on chloroquine. | Moderate |
| Rabies Immunoglobulin (RIG) | Concurrent administration is standard for Category III exposures. RIG provides immediate passive immunity; vaccine provides active immunity. Administer at different anatomical sites. | Synergistic |
7. Patient Counselling
- DO complete the entire vaccination schedule as prescribed, even if the wound has healed or the animal appears healthy.
- DO inform the doctor about any past allergic reactions to vaccines or medications.
- DO report any animal bite immediately and wash the wound thoroughly with soap and running water for 15 minutes.
- DO NOT skip or delay doses. Adherence to the schedule is critical for protection.
- DO NOT apply irritants like chili powder, turmeric, or soil to the wound.
8. Toxicology & Storage
Overdose: Unlikely to cause toxicity due to inactivated nature. Potential symptoms would be an exaggeration of local and systemic side effects (severe local reaction, high fever, significant 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). Discard any unused vaccine. Transport in a cold chain.