From the Guidelines
Recombinant monoclonal antibodies (RMAbs) for rabies post-exposure prophylaxis (PEP) should be administered as a single dose of 20 IU/kg body weight, infiltrated around and into the wound site(s) on day 0 of the PEP regimen, in conjunction with rabies vaccine. The administration protocol for RMAbs involves infiltrating the full dose around and into the wound site if anatomically feasible, with any remaining volume given intramuscularly at a site distant from the rabies vaccine administration 1. This approach is crucial for providing immediate neutralization of the rabies virus at the wound site, thereby preventing the virus from entering peripheral nerves and providing passive immunity while the vaccine stimulates active immunity. Key considerations include:
- Administration should occur as soon as possible after exposure, ideally within 24 hours, though it can still be given up to 7 days after the first vaccine dose if not initially available.
- RMAbs must always be given in conjunction with rabies vaccine, which follows a schedule of doses on days 0,3,7, and 14 (or 28 for immunocompromised patients).
- Unlike human rabies immune globulin (HRIG), RMAbs should not be administered in the same anatomical site as the vaccine.
- Products like Rabishield (rafivirumab) or Twinrab (a combination of two monoclonal antibodies) have replaced older HRIG in many settings due to their consistent potency, absence of blood-borne pathogen risk, and potentially lower cost 1. The mechanism of action of RMAbs involves immediate neutralization of the rabies virus, providing passive immunity while the vaccine stimulates active immunity, which is essential for preventing rabies after exposure.
From the Research
Administration Protocol for Recombinant Monoclonal Antibodies (RMAbs) for Post-Exposure Prophylaxis (PEP) Against Rabies
The administration protocol for RMAbs for PEP against rabies involves the following steps:
- RMAbs should be administered in conjunction with rabies vaccine as part of a PEP regimen 2, 3
- The recommended dose of RMAbs is 10 IU/kg or 20 IU/kg, depending on the specific product and study 2, 4
- RMAbs can be administered intramuscularly or in wounds, depending on the severity of the exposure 3, 4
- The primary endpoint for evaluating the efficacy of RMAbs is the ratio of the day 14 geometric mean concentration (GMC) of rabies virus neutralizing activity (RVNA) as measured by rapid fluorescent focus inhibition test 3
Safety and Tolerability of RMAbs
- RMAbs have been shown to be safe and well-tolerated in clinical trials, with similar frequency of local injection site reactions to human rabies immunoglobulin (HRIG) 2, 3
- The majority of local injection site and systemic adverse reactions reported were mild to moderate in severity 3
- RMAbs have been shown to have high neutralizing activity against rabies virus, with detectable RVNA levels from day 1 to day 21 after a single dose 4
Key Considerations for RMAbs
- RMAbs should be used in combination with rabies vaccine as part of a PEP regimen 2, 3
- RMAbs should be administered as soon as possible after exposure to rabies virus 3, 4
- The use of RMAbs as an alternative to HRIG or equine rabies immunoglobulin (ERIG) may improve access to PEP in resource-limited settings 3, 5