Safety and Immunogenicity Study of ChimeriVax West Nile Vaccine in Healthy Adults

Inclusion Criteria: * Written informed consent * Medically stable, ambulatory male or female ≥ 50 years of age. * Attend all scheduled visits and to comply with all study procedures. * Negative serum pregnancy test at Screening, and a negative urine pregnancy test on Day 0. Exclusion Criteria: * Known or suspected congenital or acquired immunodeficiency, immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term (at least 2 weeks within the previous 3 months) systemic corticosteroids therapy (at a dose of at least 10 mg of prednisone or equivalent), or depot preparation within the previous 3 months. Topical steroids are allowed. * Administration of immunoglobulins and/or any blood products within 3 months before enrollment or planned administration during treatment period of study. * Presence of acute or chronic illness associated with an oral temperature of \>38.0 °C or requiring hospitalization at time of enrollment. * Any of the following serological findings at Screening: positive Hepatitis B surface antigen (HBsAg), positive Hepatitis C (anti-HCV), or positive human immunodeficiency virus (HIV). * Personal or family history of thymic pathology (e.g., thymoma), thymectomy, or myasthenia. * History of significant allergic reaction to the vaccine components * Asplenia, functional asplenia, or any condition resulting in the absence or removal of the spleen. * Active or potentially progressive neurologic di…