Paper II
Question
Rabies vaccines and latest schedule for immunization
Answer
Modern (non-neural, cell-culture-derived) rabies vaccines: Human Diploid Cell Vaccine (HDCV), Purified Chick Embryo Cell vaccine (PCECV), and Purified Vero Cell Rabies Vaccine (PVRV) — all with markedly improved safety and immunogenicity compared to the older neural-tissue Semple vaccine.
Latest immunization schedule (post-exposure prophylaxis):
- Intramuscular (Essen) regimen — 5 doses on days 0, 3, 7, 14, and 28 (a simplified 4-dose “Zagreb”/Essen-modified regimen on days 0, 3, 7, and 14 is also WHO-recommended in many current protocols, particularly for immunocompetent individuals).
- Intradermal (ID) regimen — an updated, cost-effective WHO-recommended alternative, using a fraction of the intramuscular dose administered at multiple sites intradermally on specified days (e.g., a 2-site ID regimen on days 0, 3, 7, and 28), achieving equivalent immunogenicity at substantially lower vaccine cost — increasingly adopted in national programmes, including India, given the cost savings for mass administration.
- Category-based approach: Category II exposures — vaccine alone; Category III exposures — vaccine plus Rabies Immunoglobulin (RIG), infiltrated around the wound.
Pre-exposure prophylaxis schedule: a shortened schedule (e.g., days 0 and 7, per current WHO recommendations, a reduction from the older 3-dose schedule) for high-risk occupational groups, without RIG.