Inclusion Criteria:

• Between 18 and 50 years old
• Free of chronic medical conditions requiring ongoing therapy and in general good health as determined by a physician investigator
• Have a current (within 30 days of scheduled blood donation for this study) complete blood (cell) count (CBC) to include a Hct and Hgb that show no evidence of anemia, and total white blood cell with differential platelet counts that are within normal range, as well as hepatic enzyme (AST, ALT, LDH) values that are within normal laboratory ranges
• Negative human immunodeficiency virus (HIV) antibody test within 3 months preceding vaccination
• No evidence of pre-existing liver disease or current infection with Hepatitis A, B, or C virus as determined by serology
• No evidence for pre-existing eye disease, as determined by fundoscopic/slit lamp examination by the study ophthalmologist other than refractory changes
• No evidence by history or serologic testing for previous infection with RVF virus or RVF vaccine
• Subjects must agree to refrain from intimate contact (sexual activity), or use barrier contraception (e.g., condoms), for the 2-week period following vaccination
• Females of child-bearing potential must have a negative serum pregnancy test on screening and the morning of vaccination prior to receipt of the vaccine and must agree to use a highly effective method of birth control during the first 3 months following receipt of the MP-12 vaccine. A highly effective method of birth control is defined as one with a failure rate of less than 1% per year. Acceptable birth control methods that meet this criterion include hormonal implants and injectables (Norplant, Dep-Provera, Lunelle, and Etonogestrel); combined oral contraceptives; the intrauterine devices (IUDs) Copper T (380-A) or Mirena (Levonorgestrel Intrauterine System); female sterilization (tubal ligation); sexual abstinence; or a vasectomized partner.
• Subjects must be medically cleared for participation by an investigator
• Subjects must expect to remain in the area for the duration of the study
• Volunteer must sign an approved informed consent
• Volunteer must be willing to return for all follow-up visits including a post-vaccination ophthalmologic visit
• Volunteer must be willing to refrain from excessive (more than individual's normal routine) exercise for a period of at least 2 weeks prior to and following vaccination
• Volunteer must be willing to abstain from drinking alcoholic beverages for a period of at least 2 weeks prior to and following vaccination. Volunteer must not be a "weekend" drinker or normally drink more than 2 drinks a day if male or 1 drink a day if female.
• Volunteer must agree to report any adverse event (AE) that may or may not be associated with administration of the test article during their participation in the study.

Exclusion Criteria:

• History or evidence of liver disease/abnormality
• History of pre-existing thymic disease or thymic dysfunction (any cellular immune or antibody disorders)
• Be taking any medication, prescription or non-prescription (excluding dietary supplements), on a regular basis with the exception of contraceptive pills. This includes the regular use of statins, non-steroidal anti-inflammatory drugs (NSAIDs), immunosuppressive agents, antivirals, topical steroidal creams, and nasal sprays. Conditions requiring intermittent medications and other decisions regarding eligibility due to medication use will be deferred to physician investigators.
• Elevation above the upper limit of laboratory normal values in liver enzymes, or history of unexplained elevation in liver enzymes
• History or evidence of eye disease (excluding changes in refraction and strabismus)
• Abnormal clinical lab results indicating evidence of anemia, immunosuppression, or immune deficiency disease
• Have donated 1 unit (500 cc) or more of blood for any reason during the 2 months (56 days) preceding administration of the vaccine (as assessed by query)
• Plan to donate blood within 1 year following receipt of the vaccine
• History or evidence of previous infection with RVF or vaccination against RVF
• Any known allergies to components of the vaccine: Human serum albumin (stabilizer), Sol-U-Pro, Neomycin (antibiotic), sorbitol, L-proline, L-arginine, monosodium glutamate (MSG), or Urea
• Administration of another vaccine within 4 weeks of RVF MP-12 vaccination
• "Weekend" drinkers, males who drink more than 2 drinks a day and females who drink more than 1 drink a day, will be excluded
• Individuals who plan to start a new exercise program within two weeks of vaccination (either two weeks prior to or two weeks following vaccination) will be excluded. Individuals who are already on a regular exercise program and who have normal transaminase levels will not be excluded but will be advised not to increase their level of activity for a period of one month (for two weeks prior to until two weeks after vaccination). Individuals who do not exercise regularly and who participate in this study will be advised not to embark on an exercise program for the same time period.
• Volunteers will be cautioned against salivary contact and contact with infants, children under the age of 8 years, adults over the age of 64 years, and anyone who is immunocompromised or in poor health. Volunteers who feel unable to comply with these restrictions will be excluded from the study.