The purpose of this phase 1 study is to evaluate the safety and immunogenicity of rPA102 vaccine, using anthrax vaccine adsorbed (AVA) as a comparator.

Inclusion Criteria:

• Able to understand the study and give written informed consent. A signed informed consent must be in place before the initiation of any study interventions.
• Healthy male or female aged 18 to 40 years old (inclusive) without significant physical or clinical laboratory abnormalities.
• Two intact upper arms with sufficient intramuscular (IM) tissue in the deltoid region for vaccine administration.
• For females, negative serum pregnancy test at screening and agreement to use adequate birth control during the first 3 months of the study.
• Willingness and ability to return for all follow-up visits and blood draws for the duration of the study.
• Willingness to complete the Volunteer Diary and to report concomitant medications and adverse events (AEs) to the study site monitors during the study period.

Exclusion Criteria:

• Prior history of, or known exposure to any form of B. anthracis or any anthrax immunization.
• Member of the Armed Services (Active Duty or Reserve) since 1990, with history of previous anthrax vaccination.
• Employment in an industry involved in contact with ruminant animals, veterinary sciences, or other exposure to B. anthracis.
• Expected to be noncompliant with study visits or planning to move within 8 months.
• Body mass index of >35 or <19.
• Known allergy to aluminum hydroxide, formaldehyde, benzethonium chloride, latex, kanamycin, or any other aminoglycoside antibiotics (such as gentamycin).
• Pregnancy (positive urine pregnancy test within 24 hours prior to vaccination), or lactation.
• HIV positive (by history or screening ELISA).
• Hepatitis B or C positive (by history or screening HBsAg/anti-HCV ELISA).
• Active or past internal organ, hematologic malignancy, or metastatic cutaneous malignancy.
• History of, or current autoimmune disease, including but not limited to systemic lupus erythematosus, scleroderma, and polyarteritis.
• Immunodeficiency or unstable medical condition as determined by baseline medical history, physical exam, and laboratory assessment.
• Received, or plans to receive, licensed live vaccines within 30 days of study vaccination.
• Received, or plans to receive, licensed killed vaccines within 14 days of study vaccination.
• Received, or plans to receive, immunoglobulin or other blood products within 60 days of study vaccination.
• Received, or plans to receive, experimental drugs/vaccines within 30 days of study vaccination.
• Received, or plans to receive, systemic immunosuppresive therapy, radiation therapy, or high-dose inhaled steroids within 30 days of study vaccination.
• Use of systemic chemotherapy within 5 years prior to study.
• History of Guillain-Barre Syndrome.
• In addition to the conditions listed above, the following may qualify as a reason to exclude a volunteer from the study: fever along with moderate or serious illness within 3 days of vaccination or any condition that, in the opinion of the investigator, would render vaccination unsafe or would interfere with the study evaluations. Pending resolution of these symptoms, a volunteer may be reconsidered for vaccination.