Safety and Immunogenicity Study of Rift Valley Fever Vaccine

Inclusion Criteria: Parts A \& B: * At least 18 years old, or if active military duty, 17 years old, * Females of childbearing potential must agree to have a urine pregnancy test within 48 hours before receipt of each dose of vaccine. The test results must be negative. Females will be advised not to become pregnant for 3 months after the primary series and each booster dose, and must not be breast-feeding, * Subject must be actively enrolled in the SIP to be vaccinated at USAMRIID or be otherwise authorized (with documentation) by the DOD * Subjects must be at risk for exposure to RVF virus, * Subjects 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 may be repeated within 1 year at the discretion of the enrolling physician. * Volunteer must have signed and dated the approved informed consent (Volunteer Agreement Explanation and Affidavit). Additional Inclusion Criteria for Part B: • Completion of primary series and any follow-up titer (PRNT80) \< 1:40 from the current or a previous RVF IND 365 protocol. Exclusion Criteria Parts A \& B: * Clinically significant abnormal lab results including evidence of Hepatitis C, Hepatitis B or carrier state, or elevated liver function tests. * Personal history of immunodeficiency or current treatment with immunosuppressive medication, at the discretion of the physician. * Confirmed HIV infection. * Any medical condition that, at the discretion of the physician, may jeopardize the safety of the volunteer. * Any serious or life-threatening allergies to any component of the vaccine: formalin, human serum albumin, neomycin, streptomycin * Administration of any other vaccine within 28 days of any dose of RVF vaccine. * Any unresolved adverse event resulting from a previous immunization. Additional Exclusion Criteria for Part B: • An adequate PRNT80 (≥ 1:40) after completion of primary series.