Comparison of Safety and Immunogenicity of Purified Chick Embryo Cell Rabies Vaccine (PCECV) and Purified Vero Cell Rabies Vaccine (PVRV) Using the Thai Red Cross Intradermal Regimen at a Dose of 0.1 ML

Abstract

Intradermal (ID) vaccination with modern cell culture rabies vaccines is a means to significantly reduce the cost of post-exposure prophylaxis as compared to intramuscular vaccination. In this study we evaluated the efficacy, immunogenicity and tolerability of PCECV and PVRV administered ID in doses of 0.1 mL per site according to the 2-site Thai Red Cross (TRC) regimen. Patients with WHO category III exposure to suspect or laboratory proven rabid animals were administered either PCECV (n=58) or PVRV (n=52) ID at a dose of 0.1 mL per site on days 0, 3 and 7 and at one site on days 30 and 90. Serum samples were withdrawn on days 0, 14, 30, 90, and 180 and rabies virus neutralizing antibody (RVNA) titers were determined by rapid fluorescent focus inhibition test (RFFIT). Patients who were exposed to laboratory confirmed rabid animals were followed up for one year after exposure. All 110 patients developed RVNA titers above 0.5 IU/mL by day 14. Adequate titers >0.5 IU/mL were maintained up to day 180. Both vaccines induced equivalent RVNA titers at all time points and were well tolerated. Five subjects who were bitten by laboratory confirmed rabid dogs were alive and healthy one year after exposure. As demonstrated, PCECV and PVRV are both immunogenic, efficacious and well tolerated when administered in the TRC post-exposure prophylaxis regimen in ID doses of 0.1 mL as recommended by WHO guidelines. The use of PCECV in this regimen may prove more economical in developing countries like India.