Immunogenicity of a Two vs Three Dose, Intradermal (ID) vs Intramuscular (IM) Administration of a Licensed Rabies Vaccine for Pre-Exposure Vaccination

This is an exploratory vaccine trial to evaluate immunogenicity of a non-licensed dosing schedule and route of administration for a currently FDA licensed rabies vaccine for pre-exposure prophylaxis against rabies infection. The goal of this study is to characterize the immune response and persistence of immunity to a shortened dose schedule and intradermal (ID) administration, relative to the current licensed dosing schedule of the rabies vaccine (3 dose (0, 7, 21 days) IM). Rabies virus is endemic throughout the world due to high rates of both wild and domestic animal rabies and the risk to deployed military in endemic areas is considerable. Currently the commonly supported pre-exposure prophylaxis regimen for rabies, in the United States is comprised of three, 1.0 ml intramuscular (IM) injections of the human diploid cell vaccine (HDCV) or purified chick embryo cell (PCEC) rabies vaccine on days 0, 7, and 21 or 28. Modified, two and three dose schedules of intradermal (ID) injections of 0.1 ml of HDCV and PCEC are utilized outside the US. These two and three dose intradermal schedules share a similar safety and immunogenicity profile to intramuscular vaccinations and are easily boosted at one year after vaccination. A death, from rabies, of a US Soldier returned from Afghanistan underscores the importance of rabies pre-exposure prophylaxis for soldiers and the need to evaluate the safest, most effective means of vaccinating large deploying forces. While the current three dose, 1 ml IM rabies series is effective, a shortened, equally effective vaccination series with significantly smaller dose per injection would greatly improve the logistics and cost associated with universal or even targeted coverage of deploying soldiers. Evaluation of a shorter, smaller-dose, pre-exposure vaccination series for rabies is the goal of this study.