The purposes of this study is to evaluate and compare the safety, reactogenicity, and tolerability of the PA83-FhCMB vaccine candidate delivered at 4 dose levels with Alhydrogel

Inclusion Criteria:

• Citizen or permanent resident of the US

• Male or female aged 18 to 49 years inclusive

• Able to give written informed consent

• Healthy, as determined by medical history, physical examination, vital signs, and clinical safety laboratory examinations at baseline

• Females should fulfill one of the following criteria:

  1. At least one year post-menopausal
  2. Surgically sterile
  3. Willing to use a medically approved form of contraception (eg, oral, implantable, transdermal, or injectable hormonal contraceptive; intrauterine device; barrier protection to include female condom, diaphragm, cervical cap, or male condoms in conjunction with spermicide) for 30 days prior to first vaccination and through the end of the study
  4. Willing to abstain from sexual intercourse for 30 days prior to first vaccination and through the end of the study

• Women of childbearing potential must have a negative urine pregnancy test within 24 hours preceding receipt of each dose

• Comprehension of the study requirements

• Expressed availability for the required study period

• Ability to attend scheduled visits and to be contacted by telephone throughout the follow-up period

Exclusion Criteria:

• History of anthrax disease or receipt of anthrax vaccine

• Presence of significant uncontrolled medical or psychiatric illness (acute or chronic) including institution of new medical or surgical treatment or a significant dose alteration for uncontrolled symptoms or drug toxicity within 3 months of screening

• Positive serology for HIV-1 or HIV-2, or HBsAg or HCV antibodies

• Pregnancy or lactation

• Cancer or treatment for cancer, within the previous 3 years, excluding basal cell carcinoma

• Presence of any medical condition that may be associated with impaired immune responsiveness, including diabetes mellitus, per the investigator's discretion

• Presently receiving or history of receiving, during the preceding 3-month period, any medications or other treatments that may adversely affect the immune system

  1. This includes allergy injections, immune globulin, interferon, immunomodulators, cytotoxic drugs, or systemic corticosteroids (oral or injectable; 20 mg/day x 14 days or longer)
  2. Radiation therapy
  3. Intranasal and topical corticosteroids will be allowed

• Receipt or planned administration of a non study vaccine within 14 days prior to vaccination and throughout the study period (30 days for live vaccines) Immunization on an emergency basis with Tetanus Toxoids Adsorbed for adult use (Td or Tdap) or influenza vaccine up to 14 days before or at least 14 days after a dose of study vaccine will be allowed

• History of anaphylactic type reaction to injected vaccines

• History of drug or chemical abuse in the year before the study

• Receipt of any investigational product or nonregistered drug within 30 days prior to vaccination or currently enrolled in any investigational drug study or intends to enroll in such a study within the ensuing study period

• Receipt of blood or blood products 8 weeks prior to vaccination or planned administration during the study period

• Donation of blood or blood products within 8 weeks prior to vaccination or at any time during the study

• Acute disease within 72 hours prior to vaccination

  1. Acute disease is defined as the presence of a moderate or severe illness (as determined by the Investigator through medical history and physical examination) with or without fever (≥38°C; 100.4°F), or an oral temperature of ≥38°C orally
  2. Study vaccine can be administered to persons with a minor illness

• History of immunodeficiency, chronic illness requiring continuous or frequent medical intervention, autoimmune disease, use of immunosuppressive medications, or ongoing therapy with systemic corticosteroids within 3 months prior to any planned vaccine dose. Inhaled and topical steroids are permitted. "Burst" therapy of steroids is permitted except within 2 weeks prior to vaccination.

• Evidence of psychiatric, medical and/or substance abuse problems during the past 6 months that the investigator believes would adversely affect the subject's ability to participate in the trial

• Occupational or other responsibilities that would prevent completion of participation in the trial, including:

  1. US military or reservists who may receive the licensed anthrax vaccine (BioThrax) or served during the Persian Gulf War between January and May, 1991. Such individuals may be enrolled only if they provide their medical records, which can then show proof that they have not received the licensed anthrax vaccine.
  2. Postal and other workers who may be exposed to anthrax or may have to take BioThrax

• Any condition that, in the opinion of the investigator, might interfere with interpretation of data supporting the primary study objectives