Biological warfare remains a constant threat to U.S. forces. Anthrax has been identified as the primary biological weapon facing American service men and women today. The greatest concern is inhalation anthrax; the form of anthrax that is expected following an attack with aerosolized anthrax spores. This is 99 percent lethal for unvaccinated individuals. After a 3 year study, the Secretary of Defense William S. Cohen concluded that anthrax vaccination, used with other protective measures such as detectors and protective gear, is the safest way to protect highly mobile U.S. military forces against inhalation anthrax. In March 1998, DoD began immunizing personnel deploying to or stationed in high threat areas, currently defined as Southwest Asia and the Korean Peninsula, and their contiguous waters. Over the next five years, all active and Reserve personnel will be immunized using a prioritized vaccination schedule.

Anthrax Vaccine: a historical perspective

The anthrax vaccine used by the U.S. military was approved and licensed by the Food and Drug Administration in 1970. It is the same vaccine used by civilians in occupations at increased risk of contracting anthrax, such as veterinarians, animal handlers, and wool sorters. The vaccine is now being manufactured by BioPort Corporation (formerly the Michigan Biologic Products Institute). It is made from a culture of attenuated strains of anthrax that is filtered, so that it contains predominantly a protective antigen. There are no whole bacteria in the product, and it is impossible to contract the disease from the vaccine.

The vaccine was originally developed to protect against cutaneous anthrax, but in the studies for FDA-licensure, there were 5 cases of inhalation anthrax in the placebo group and no cases of inhalation anthrax in the vaccinated group. However, there were not enough inhalation anthrax cases to prove efficacy against an inhalation challenge. To show the effectiveness of the vaccine in preventing disease after an aerosol challenge, animal studies using Rhesus monkeys have been performed. In three separate studies, using a total of 43 monkeys who received either one or two doses of the vaccine, and received an aerosol challenge 90 to 400 times the lethal dose, only one monkey died while the other 42 survived.

Recommended vaccination schedule

6 subcutaneous, 0. 5 ml doses should be given on days 0, 2 weeks, 4 weeks, 6 months, 12 months, and 18 months, followed by annual booster dose to maintain immunity. If an individual is late for their next dose, the series will not need to be restarted unless more than 2 years have elapsed between doses one and two. Otherwise, simply give the next dose in the series as soon as possible, with administration of subsequent doses based on the required intervals from the last dose given.

Administration of the anthrax vaccine (like all other vaccines) will be documented in three locations: the medical record on the SF-601 (Anthrax Immunization Record overprint), the yellow shot card (PHS-731), and in the automated immunization tracking system (currently SAMS (Shipboard Automated Medical System)). Required data elements are listed in references (a) and (b). Reference (a) outlines procedures for ordering anthrax vaccine.

Immunization site reactions can include soreness, redness, and localized swelling (resolution occurs within hours to days). About thirty percent of individuals who receive the anthrax immunization will develop a non-tender subcutaneous nodule that will resolve on its own within a few weeks to months. There have been no long term sequelae or side effects from this vaccine. Adverse reactions to the anthrax vaccine that result in hospitalization, lost work time greater than 24 hours, or suspected lot contamination must be reported on the Health and Human Services' Vaccine Adverse Event Reporting System (VAERS) form, which is sent to the Navy Environmental Health Center (NEHC). However, at the discretion of the provider or patient, any adverse event can be reported using the VAERS form. Information on how to complete VAERS can be found in references (a), (b), and (c).