Safety, Tolerability and Immunogenicity of Recombinant Anthrax Vaccine Compared With Anthrax Vaccine Adsorbed

Anthrax is a zoonotic disease, occurring in wild and domestic mammals, caused by the spore-forming bacterium Bacillus anthracis (B. anthracis). Anthrax occurs in humans when they are exposed to infected animals, tissue from infected animals or when they are directly exposed to B. anthracis or its spores. Depending on the route of infection, anthrax disease can occur in three forms: cutaneous, gastrointestinal, and inhalation. In the United States of America (USA), the annual incidence of human anthrax has declined from approximately 130 cases annually in the early 1900s to no cases during 1999 to 2000. However, in the USA, shortly after September 11th, 2001, there were 22 cases (18 confirmed) of inhaled and cutaneous anthrax infection that were related to contaminated mail. The development of a new anthrax vaccine is necessary because the current AVA vaccine requires the growth of B. anthracis in its manufacturing process and has a complex administration regimen of six administrators of vaccine in 18 months. As protective antigen (PA) is a central virulence factor in anthrax pathogenesis and a major immunogen in the current vaccine, a recombinant, acellular, protective antigen-based anthrax vaccine, could offer an improved manufacturing process and a simpler dosing schedule. Furthermore, the vaccine could offer improved protection against inhaled B. anthracis, and could, when used in conjunction with antibiotics, form part of the management of anthrax exposed individuals. This is a dose ranging study comparing different primary vaccine schedules of rPA Anthrax vaccine to the licensed dose of Anthrax Vaccine Adsorbed. The study is designed to measure the immune response, and to evaluate the safety and tolerability of different doses of rPA Anthrax Vaccine. After subjects have given informed consent, they will undergo physical exams, medical history screening, pregnancy tests, ECG, HIV, Hepatitis B \& C tests, safety blood tests, and urine drug and alcohol screen. Subjects will be asked to complete a diary card to record any symptoms they may experience. The subjects that receive AVA will be offered the opportunity to complete the licensed course of vaccination which would involve AVA vaccinations at 6, 12 and 18 months.