Pre-Exposure Prophylaxis

In a controlled field study conducted from 1955-1959 using an earlier version of a protective antigen-based anthrax vaccine, the calculated efficacy of the vaccine to prevent all types of anthrax disease combined was 92.5% (lower 95% CI = 65%). The efficacy analysis in this study included all cases of anthrax disease, regardless of the route of exposure or manifestation of the disease10.

This study included 1,249 workers [379 received anthrax vaccine, 414 received placebo, 116 received incomplete inoculations (with either vaccine or placebo) and 340 were in the observational group (no treatment)] in four mills in the northeastern United States that processed imported animal hides.

Prior to vaccination, the yearly average number of human anthrax cases (both cutaneous and inhalational) was 1.2 cases per 100 employees in these mills. During the trial, 26 cases of anthrax were reported across the four mills – 5 inhalation and 21 cutaneous. Of the five inhalation cases (four of which were fatal), two received placebo and three were in the observational group. Of the 21 cutaneous cases, 15 received placebo, three were in the observational group, and three received anthrax vaccine. Of those three cases in the vaccine group, one case occurred just prior to administration of the scheduled third dose, one case occurred 13 months after an individual received the third of the scheduled 6 doses (but no subsequent doses), and one case occurred prior to receiving the scheduled fourth dose of vaccine.

The safety and efficacy of BioThrax have not been established in pediatric or geriatric populations.

BioThrax may not protect all individuals vaccinated, particularly patients with impaired immune responses due to congenital or acquired immunodeficiency or immunosuppressive therapy. Individuals are not considered protected until they have completed the three-dose primary vaccination series.

10 Brachman, P., et al., 1962. Field evaluation of a human anthrax vaccine. Amer. J. Public Health, 52:632-645.

Next: Time to Protection




BioThrax is a vaccine indicated for the active immunization for the prevention of disease caused by Bacillus anthracis in persons 18 through 65 years of age. BioThrax is approved for:

  1. Pre-exposure prophylaxis of disease in persons at high risk of exposure.
  2. Post-exposure prophylaxis of disease following suspected or confirmed Bacillus anthracis exposure, when administered in conjunction with recommended antibacterial drugs.

The efficacy of BioThrax for post-exposure prophylaxis is based solely on studies in animal models of inhalational anthrax.


Severe allergic reaction (e.g. anaphylaxis) after a previous dose of BioThrax or a component of the vaccine.

Adverse Reactions

The most common (≥10%) local (injection-site) adverse reactions observed in clinical studies were tenderness, pain, erythema, edema, and arm motion limitation. The most common (≥5%) systemic adverse reactions were muscle aches, headache, and fatigue. Acute allergic reactions, including anaphylaxis, have occurred with BioThrax.

Warnings and Precautions

Vaccination with BioThrax should be avoided by individuals with a history of anaphylactic or anaphylactic-like reaction following a previous dose of BioThrax or any component of the vaccine. If BioThrax is used during pregnancy, or if the patient becomes pregnant during the immunization series, the patient should be apprised of the potential hazard to the fetus. Pregnant women should not be vaccinated unless the potential benefits of vaccination have been determined to outweigh the potential risk to the fetus. It is not known whether BioThrax is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when BioThrax is administered to a nursing woman.

BioThrax should be administered with caution to persons with a possible history of latex sensitivity since the vial stopper contains dry natural rubber.