The FDA has approved the use of BioThrax (Anthrax Vaccine Adsorbed) to prevent disease following suspected or confirmed exposure to the anthrax bacteria Bacillus anthracis, which causes the deadly disease. Although anthrax affects mostly animals, it is contagious and can be transmitted to humans through contact or consumption of infected meat as well as by inhaling the spores, themselves. In fact, the hardiness of anthrax spores (not to mention their ease of production in vitro, make them extremely “well-suited” to use as biological weapons in powdered or aerosol form. According to the CDC such bio-weapons have turned up in at least 5-state programs found in the US, United Kingdom, Russia, Japan and Iraq.
Up until now, there haven’t been any effective vaccines against anthrax, although some forms of the disease respond well to antibiotic treatment. This makes BioThrax the first vaccine to receive approval based on the Animal Rule, which allows animal efficacy data to be used as a basis for approval when human efficacy studies are not ethical or feasible. The vaccine’s new use is approved for people 18 through 65 years of age in conjunction with recommended antibiotic treatment.
“With this month’s approval of BioThrax, we now have a vaccine that can be used, together with antibiotic treatment, to prevent disease after exposure to anthrax spores,” stated Karen Midthun, M.D., director of the FDA’s Center for Biologics Evaluation and Research, who also noted that. BioThrax was initially approved by the FDA in 1970 for the prevention of anthrax disease in persons at high risk of exposure.
The ability of BioThrax to increase the probability of survival after stopping post-exposure antibiotic treatment was assessed in rabbits. Rabbits treated with both antibiotics and BioThrax had a survival rate of 70%-100%, depending on the vaccine dose administered. In contrast, in 2 studies of rabbits that received only antibiotic treatment, survival rates were 44% and 23% respectively.
The safety and antibody responses to BioThrax in humans were evaluated in a multi-center study conducted in the United States. Subcutaneous (under the skin) injections were given to 200 healthy adults in three doses at zero, 2. and 4- weeks. The majority of study participants generated antibody responses that correlated to a 70% probability of survival that was observed in animal models.
The observed adverse reactions were tenderness, pain, swelling, and redness at the injection site, as well as limited movement of the injected arm. The most common systemic adverse reactions were muscle aches, headache, and fatigue.