Simulated post-exposure rabies vaccination with purified chick embryo cell vaccine using a modified Thai Red Cross regimen

AbstractObjectives: Currently, two intradermal regimens for the administration of cell culture rabies vaccines are approved by the WHO for rabies post-exposure prophylaxis: the two site Thai Red Cross regimen (TRC) and the eight site regimen. For the TRC regimen the volume of vaccine recommended per dose is 0.1ml of purified Vero cell rabies vaccine (PVRV) and 0.2ml of purified chick embryo cell vaccine (PCEC). The objective of the present study was to evaluate comparatively the immune response to PCEC and PVRV vaccines administered by the TRC regimen using a uniform dose of 0.1ml of vaccine.Methods: Forty-two subjects received TRC regimen (2-2-2-0-1-1) with 0.1ml of PCEC vaccine and 38 subjects received the same regimen with PVRV. The rabies neutralizing antibody response in these subjects on days 10, 28, 90 and 180 was determined by the standard mouse neutralization test (MNT).Results: There was adequate antibody response with both the vaccines and 100% seroconversion was observed by day 10. Furthermore, the antibody titers obtained with PCEC did not differ significantly from those obtained with PVRV on all days tested (p>0.05).Conclusions: It can be concluded from the results that an adequate antibody response can be obtained with PCEC vaccine when administered by the TRC regimen even after reducing the quantity of vaccine from 0.2ml to 0.1ml per intradermal dose. The feasibility of using this regimen in true post-exposure cases needs to be further evaluated