"Anthrax is highly lethal and relatively easy to produce in large quantities for use as a weapon. Anthrax spores are easily spread in the air over a large area and can be stored and remain viable for a long time. For this reason, anthrax may be the most important biological warfare threat facing U.S. forces. The intelligence community believes several countries currently have or are developing an offensive biological warfare capability using anthrax. However, given the ease with which anthrax can be produced, the threat could come from anywhere. For that reason, U.S. Forces may have little or no warning before an anthrax attack, which could be delivered by unconventional means. As a result, U.S. military forces around the world face a very real threat of a surprise anthrax attack. On February 24, 2004, CIA Director George Tenet told the Senate Select Intelligence Committee: 'Although gaps in our understanding remain, we see al-Qaeda's program to produce anthrax as one of the most immediate terrorist CBRN [chemical, biological, radiological, nuclear] threats we are likely to face.'"
Anthrax Vaccine Immunization Program: http://www.anthrax.osd.mil/