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Few Workers Need Routine Protection Against Anthrax, Immunization Group Says

Cheryl A. Thompson

Routine vaccination against anthrax in the United States is recommended only for workers who come in contact with imported animal hides and wool likely to harbor Bacillus anthracis spores and for laboratory personnel who work with large amounts of the bacteria, a federal advisory group stated in December.

The Advisory Committee on Immunization Practices (ACIP), in its recommendations on the domestic use of the only anthrax vaccine licensed for sale in the United States, noted that "emergency first responders" and other groups initially considered for vaccination in advance of a terrorist attack involving a biological weapon are no longer candidates. Because no credible organization or group has determined which population would be the target of a terrorist release of B. anthracis spores, and the risk of exposure cannot be calculated, ACIP concluded that preexposure vaccination is unnecessary. However, people about to enter an area where B. anthracis had earlier been released could be at risk for exposure and might need prophylaxis with an antimicrobial, with or without the vaccine.

Although not effective against the spores, certain antimicrobials can prevent B. anthracis from germinating, thus delaying the onset of anthrax. FDA recently approved the use of ciprofloxacin to prevent the development or progression of inhalation anthrax after exposure to B. anthracis spores. Penicillin and doxycycline have FDA-approved labeling for use in the treatment of anthrax unrelated to biological warfare.

ACIP, which counsels the Centers for Disease Control and Prevention, issued its recommendations on the basis of information collected from studies of animals, laboratory and textile-mill workers, and military personnel. The recommendations pertain only to aluminum hydroxide-adsorbed cell-free anthrax vaccine, currently manufactured by Michigan-based BioPort.

In addition to advice, the recommendations provide an overview of anthrax, a disease that can spread by skin contact, ingestion, or inhalation of B. anthracis spores originating from infected animals. Domestic and wild animals in the United States have been reported to harbor B. anthracis, but the incidence of infection is unknown. The most recent confirmed case of human anthrax in the United States was reported in 1992; the person had cutaneous anthrax. A case of inhalation anthrax has not been reported in the United States since 1976.

Although the risk of infection with naturally occurring anthrax seems remote, various groups including the government consider B. anthracis one of the most likely agents to be used in biological warfare. Ease of respiratory transmission, inhalation anthrax’s high mortality rate (>85%), and the spore’s stability make B. anthracis a potent weapon.

The recommendations were published in the Recommendations and Reports supplement (PDF) to the December 15, 2000, issue of Morbidity and Mortality Weekly Report.

Military Use of Anthrax Vaccine Slows; Congress Wants Information on Safety 

A dwindling supply of anthrax vaccine has caused the Department of Defense (DoD) to slow its immunization program.

Problems with production of the vaccine by BioPort, the only U.S. firm manufacturing the product, continue to linger. As a result, DoD announced in November 2000 that only U.S. service members assigned to duty in Southwest Asia, where exposure to a terrorist release of B. anthracis spores is considered to be the greatest, would receive the vaccine. Full resumption of DoD’s effort to vaccinate at-risk service members would resume once production problems have been resolved to the satisfaction of FDA.

DoD’s vaccination effort has also been affected by Congress. The department’s appropriations bill for the current fiscal year requires the defense secretary to submit to congressional committees information on FDA approval of the vaccine’s production and on events that might result from continuing to rely on BioPort for the supply. Also, the defense secretary must implement a system for monitoring program participants’ adverse reactions to the vaccine.