Inclusion Criteria:

• Able to Understand and give informed consent

  • Age 18-45 years
  • Agrees not to take any vaccines within 30 days before or 30 days after yellow fever vaccination.
  • Women of child bearing potential must agree to use effective birth control throughout the duration of the study. A negative urine pregnancy test must be documented prior to vaccination.

Exclusion Criteria:

• Travel to or having lived in a country/area which is endemic for yellow fever.

  • History of previous yellow fever, West Nile, Dengue, St Louis encephalitis, Japanese encephalitis vaccination or infection
  • Any history of allergy to eggs, chicken or gelatin or to any previous vaccine
  • History of HIV infection, Hepatitis B or Hepatitis C infection
  • History of any chronic meci al conditions that are considered progressive (ex.diabetes, heart disease, lung disease, liver disease, kidney disease, auto immune diseases, gastrointestinal diseases and uncontrolled hypertension).
  • Use of systemic immunosuppressive medications (ex. prednisone) for 2 weeks or more in the past 3 months
  • History of excessive alcohol consumption, drug abuse, psychiatric conditions, social conditions or occupational conditions that, in the opinion of the investigator, would preclude compliance with the trial.
  • Recept of any live or inactivated vaccine within 30 eays of a vaccination visit.
  • Thymus gland problems (such as myasthenia gravis, DiGeorge syndrome, thymoma) or removal of thymus gland.
  • Receipt of blood products or immune globulin product within 42 days of the vaccination visit.
  • Pregnant women and nursing mothers or women who are planning to become pregnant for the study duration.
  • Any condition in the opinion of the investigator that would interfere with the proper conduct of the trial.