Safety and immunogenicity of rabies pre- and postexposure intradermal regimens using Abhayrab, a purified vero cell rabies vaccine (PVRV) produced in India in healthy volunteers: towards greater affordability of rabies prophylaxis

Abstract Background: Rabies is 100% fatal, but is preventable. However, due to the high cost of vaccines and immunoglobulins, as well as their limited availability, many dog-bite victims in the Philippines do not complete the required PEP regimen. This concern may be addressed by the introduction of various new brands of affordable rabies vaccines and biologicals for use with the ID regimen. Objective: Study the safety and immunogenicity of rabies pre- and post-exposure intradermal regimens using Abhayrab, a purified vero cell rabies vaccine (PVRV) produced by the human biological institute of Ooty India in healthy volunteers. Methods: In a randomized, single blind, unicentric trial, 149 healthy volunteers (5 - 50 years in age) were recruited to the study. The subjects were then randomized into two groups. Group 1 (pre-exposure) (73 subjects) followed the standard ID regimen using a dose of 0.1 mL PVRV (Abhayrab) given intradermally on either deltoid on days 0, 7 and 28. Group 2 (post-exposure) (76 Subjects) followed the modified Thai Red Cross ID regimen (2-2-2-0-2) using a dose of 0.1 mL PVRV (Abhayrab) each given intradermally on both deltoids on days 0, 3, 7, and 28. Following administration of vaccine, subjects were observed closely for 30 minutes at the site for adverse reactions. Four ml of blood from each subject was drawn on days 0, 14, and 28 for anti-rabies antibody titres. Safety and immunogenicity were assessed through follow-up of adverse events and anti rabies antibody response, respectively. Results: Eventually, 120 subjects, 60 in each group, completed the day 28 ID immunization. All the 120 subjects demonstrated seroconversions with antibody titers greater than the WHO recommended cut-off level of 0.5 IU/mL on days 14 and 28. The GMC values for Group 1 were 3.30 IU/ml and 4.37 IU/mL on days 14 and 28, respectively, while those of Group 2 were 3.73 IU/mL and 4.82 IU/mL, respectively. These GMC values were within their 95% CIs. Only a few mild adverse events were observed with no incidences of moderate or severe events. Conclusion: Abhayrab is a safe and immunogenic rabies vaccine when administered intradermally.