Phase 2 Safety and Immunogenicity Study of Rift Valley Fever Vaccine

Inclusion Criteria: * Be 18 to 65 years old at time of consent. * Have RVF plaque reduction neutralization 80% titers (PRNT80) \<1:10 for primary series. * Have RVF PRNT80 (plaque reduction neutralization 80% titer) \<1:40 for booster series. * If female of childbearing potential, must agree to have a urine pregnancy test on the same day before each vaccine administration. (Exception: documented hysterectomy or ≥3 years of menopause.) The results must be negative. Females must agree not to become pregnant for 3 months after receipt of the last study treatment (vaccination). * Be considered at risk for exposure to RVF virus and who have submitted a Request for IND Vaccines for the RVF vaccine. * Sign and date the approved informed consent document and HIPAA Authorization. * Have in their charts: * medical history (including concomitant medications) within 60 days of planned first administration of vaccine * physical examination and laboratory tests within 1 year * previous chest radiograph results and electrocardiogram * Be medically cleared for participation by an investigator. (Examinations and/or tests may be repeated at the discretion of the PI.) * Be willing to return for all follow-up visits. * Agree to report any adverse events (AEs) that may or may not be associated with administration of the vaccine for at least 28 days after administration and agree to report all serious adverse events (for example, resulting in hospitalization) for the duration of the subject's participation in the study. * Agree to defer blood donation for 1 year after receipt of the vaccine Exclusion Criteria: * Have completed previous RVF vaccine study as a nonresponder (PRNT80 \<1:40). * Have clinically significant abnormal laboratory results (including evidence of hepatitis C, hepatitis B carrier state) or elevated liver function tests (two times the normal range or at the discretion of the PI). * Have a personal history of an immunodeficiency or received treatment with an immunosuppressive medication, such as systemically administered glucocorticoids (eg prednisone) within 1 month before planned administration of the vaccine or with other immunosuppressive therapies within 6 months of planned administration of the vaccine. Other immunosuppressive therapies include all cancer chemotherapeutic agents, drugs to prevent transplant rejection, interferons, monoclonal antibodies, protein kinase inhibitors, methotrexate, TNF (tumor necrosis factor) inhibitors, and any other drug determined to be immunosuppressive by the PI. Current administration of topical, inhalational, or intranasal glucocorticoids is not excluded. * Have confirmed HIV infection. * Have positive pregnancy test or be breastfeeding female. * Have any known allergies to components of the vaccine: * Fetal rhesus monkey lung cells * Formaldehyde * Neomycin sulfate * Streptomycin * Sodium bisulfite * Human serum albumin (HAS) * RVF virus (Entebbe strain) * Have administration of another vaccine or investigational product within 28 days of RVF vaccination. * Have any unresolved AE resulting from a previous immunization. * Have a medical condition that, in the judgment of the PI, would impact subject safety.