Rabies post-exposure prophylaxis vaccination with purified chick embryo cell vaccine (PCECV) and purified vero cell rabies vaccine (PVRV) in a four-site intradermal schedule (4-0-2-0-1-1): An immunogenic, cost-effective and practical regimen

Abstract

Currently, two intradermal (ID) regimens for rabies post-exposure prophylaxis (PEP) are recommended by WHO and used in countries where approved by national authorities: the Thai Red Cross (TRC) two-site ID regimen and the eight-site ID regimen. Besides these WHO recommended schedules, a new economical four-site ID regimen was evaluated that reduces the cost of PEP by up to 80%, when compared with the standard intramuscular Essen regimen, reduces the number of visits required for the patients when compared with the TRC regimen, and is more convenient than the eight-site regimen. To determine the immunogenicity of the ID four-site PEP regimen (4-0-2-0-1-1), 180 healthy volunteers were randomized to receive 0.1 mL volumes of PCECV or PVRV administered ID over both left and right shoulders and both deltoid regions on day 0, both deltoid regions on day 7 and over one deltoid region on days 30 and 90. Regardless of the vaccine, every subject developed rabies virus neutralizing antibody (RVNA) titers above 0.5 IU/mL by day 14, as determined by rapid fluorescent focus inhibition test (RFFIT) using a homologous test system. Two weeks after the last dose of vaccine, RVNA titers were all above 0.5 IU/mL (day 104). Geometric mean titers were similar throughout the study period. Both vaccines were well tolerated. These results demonstrate that a new four-site ID PEP regimen is a cost-effective and convenient alternative to IM (Essen or Zagreb) or ID (TRC or eight-site) regimens, especially using a 1 mL vial of vaccine (PCECV).