Anthrax Vaccine Adsorbed (AVA) was licensed in 1970 to provide protection against infection with Bacillus anthracis. AVA was initially administered on a limited basis, primarily to protect veterinarians and workers processing animal products such as hair or hides that could be contaminated with anthrax spores. In the 1990s, with growing concerns about the possible use of anthrax as a biological weapon, use of the vaccine was substantially expanded. The Department of Defense (DoD) vaccinated some of the military personnel deployed for the Gulf War in 1991 and in 1998 initiated the Anthrax Vaccine Immunization Program, calling for mandatory vaccination of all U.S. service members. By late 2001, roughly 2.1 million doses of AVA had been administered. Production of AVA was suspended in 1998 when the facility manufacturing the vaccine was closed for renovations, which were undertaken to meet regulatory requirements of the Food and Drug Administration (FDA). Concerns about the efficacy and safety of AVA, and about vaccine production, led Congress to direct the DoD to support an independent examination of AVA by the Institute of Medicine. In October 2000, the Institute of Medicine convened the Committee to Assess the Safety and Efficacy of the Anthrax Vaccine. The committee reviewed all available data, both published and unpublished, and heard from representatives of DoD, FDA, and other federal agencies; from the vaccine manufacturer BioPort; from researchers studying the efficacy and safety of the vaccine; and from service members and others with concerns about the safety or efficacy of the vaccine. After the bioterrorism of fall 2001, the committee accelerated its original timetable for its review. As indicated by evidence from studies in both humans and animals, the committee concluded that AVA, as licensed, is an effective vaccine to protect humans against anthrax, including inhalational anthrax.