RIG Administration During Ongoing PEP: WHO and Indian NRCP-Aligned Guidance
For Scenario 1, RIG should be administered immediately for the new Category III exposure, even though the patient is already receiving vaccine for the initial Category II exposure. For Scenario 2, RIG should NOT be repeated for the second Category III exposure if it was already given at the start of the current PEP series. 1, 2, 3
Scenario 1: Category II → New Category III During PEP (No Initial RIG)
Administer RIG immediately for the new Category III exposure, along with continuing the vaccine series. 1, 2, 3
Rationale and Protocol:
RIG indication is based on the current exposure category, not the vaccination status during an ongoing series. A new Category III exposure (transdermal bite or scratch, or mucous membrane contamination) requires passive immunization regardless of active vaccination already in progress. 1, 2, 3
RIG can be administered up to and including Day 7 of the vaccine series if it was not given initially. Since your patient is on Day 15 of their original series but Day 0 of the new Category III exposure, this represents a new exposure requiring its own RIG administration. 1, 4
Administer 20 IU/kg body weight of human RIG (HRIG) or equine RIG (ERIG), infiltrating the full calculated dose into and around all wounds from the new Category III exposure if anatomically feasible. Any remaining volume should be given intramuscularly at a site distant from vaccine administration. 1, 2, 3
Continue the vaccine series according to the Thai Red Cross intradermal regimen (0.1 mL ID at 2 sites on days 0,3,7,28). The patient should complete their original schedule while ensuring adequate coverage for the new exposure. 4
Critical Pitfall to Avoid:
- Never withhold RIG for a Category III exposure simply because the patient is already receiving vaccine. The combination of RIG and vaccine is essential for severe exposures, as RIG provides immediate passive immunity while vaccine-induced active immunity develops over 7-14 days. 5, 1, 2
Scenario 2: Category III → New Category III During Same PEP Course (RIG Already Given)
Do NOT administer RIG again for the second Category III exposure. RIG is given only once per PEP course. 1, 2, 3
Rationale and Protocol:
RIG must be given only once during any single PEP course, regardless of subsequent exposures during that period. By Day 15, the patient has already developed active immunity from the vaccine series (doses on Days 0,3,7 completed), making additional passive immunization unnecessary and potentially harmful. 1, 2, 3
Exceeding the recommended 20 IU/kg dose of RIG can suppress active antibody production from the vaccine. Administering a second dose of RIG would effectively double the passive antibody load and interfere with the ongoing immune response. 1, 2, 3
For the new Category III exposure on Day 15: Provide thorough wound care (wash for 15 minutes with soap and water, apply virucidal agent like povidone-iodine), ensure the patient completes the full vaccine series on schedule (Day 28 dose still pending), and consider whether the exposure warrants restarting or extending the vaccine series in consultation with local health authorities. 1, 2
The patient's existing vaccine-induced immunity should provide protection against the new exposure, as rabies virus neutralizing antibodies are typically detectable by Day 7-14 of the vaccine series. 5
Critical Pitfall to Avoid:
- Never repeat RIG administration during the same PEP course. This is explicitly contraindicated as it may suppress the active immune response that has already been initiated. 1, 2, 3
RIG Indication: Independent of Vaccine Route (ID vs IM)
RIG indication and dosing are identical regardless of whether the intradermal (Thai Red Cross) or intramuscular (Essen/CDC) vaccine regimen is used. 1, 2, 3, 4
Key Principles:
RIG indication depends solely on exposure category (WHO Category III), not on vaccine route. Both ID and IM regimens require RIG at 20 IU/kg for Category III exposures in previously unvaccinated persons. 1, 2, 3, 4
The Thai Red Cross intradermal regimen has been validated with RIG administration in multiple studies and is WHO-approved. The timing and dosing of RIG remain the same: administer on Day 0 with the first vaccine dose, infiltrate wounds, and give any remaining volume intramuscularly at a site distant from vaccine injection. 5, 4
Both regimens achieve adequate rabies virus neutralizing antibody levels when combined with RIG for Category III exposures. The ID regimen uses less vaccine volume (0.1 mL at 2 sites vs 1.0 mL IM) but provides equivalent immunogenicity. 5, 4
WHO and Indian NRCP Alignment:
WHO guidelines specify RIG for Category III exposures regardless of vaccine regimen. The Indian National Rabies Control Programme follows WHO recommendations and explicitly endorses both the Thai Red Cross ID regimen and the Essen IM regimen, with identical RIG protocols for both. 5, 1, 2, 4
Never administer RIG and vaccine at the same anatomical site, as this may interfere with vaccine immunogenicity. This applies to both ID and IM regimens. 1, 6, 2, 3
Summary Algorithm for RIG Decision-Making
For any new Category III exposure during ongoing PEP: