Safety and Immunogenicity Study of Rift Valley Fever Vaccine, Inactivated

Inclusion Criteria: 1. At least 18 years old. 2. Females of childbearing potential must have a negative serum or urine pregnancy test within 48 hours before each vaccination. Females will be advised not to become pregnant for 3 months after the primary series and each booster dose. 3. Females must not be breast-feeding. 4. Subject must be at risk for exposure to RVF virus. 5. Subject must have an up-to-date (within 1 year) medical history, physical examination, and laboratory tests in their charts and be medically cleared for participation by an investigator. Examinations or tests to qualify for enrollment may be repeated at the discretion of the investigators. 6. Subject must sign and date the approved informed consent document. 7. For initiation of primary series, RVF PRNT80 \<1:10. 8. For RE-ENTRY into this protocol or ROLLOVER from an earlier RVF protocol to receive a booster, RVF PRNT80 \<1:40 within past 1 year Exclusion Criteria: 1. Older than 65 years of age for the primary series vaccination (able to receive booster doses if no other contraindications). 2. Clinically significant abnormal lab results, including evidence of Hepatitis C, Hepatitis B carrier state, or elevated (2 times normal) liver function tests. 3. Personal history of immunodeficiency or current treatment with immunosuppressive medication. 4. Confirmed positive human immunodeficiency virus (HIV) titer. 5. Any medical condition that, at the discretion of the physician, may jeopardize the safety of the subject. 6. Any serious or life-threatening allergies to any component of the vaccine: formalin human serum albumin neomycin streptomycin fetal rhesus lung cells RVF virus inactivated 7. Administration of any Investigational New Drug (IND) product or any vaccine within the 28 days before RVF vaccination. 8. Any unresolved adverse event resulting from a previous immunization.