Safety and Immunogenicity of Formulations of Dengue Vaccines in Healthy Flavivirus-Naïve Adults

Inclusion Criteria : * Healthy as determined by medical history, clinical examination, and biological safety parameters * Aged 18 to 45 years on the day of inclusion. * Informed consent form signed. * Able to attend all scheduled visits and to comply with all trial procedures * For a woman of child-bearing potential, use of an effective method of contraception or abstinence for at least 4 weeks prior to the first vaccination and at least 4 weeks after the last vaccination. Exclusion Criteria : * History of thymic diseases or thymectomy. * For a woman of child-bearing potential, known or suspected pregnancy or positive pregnancy test * Breast-feeding * Current abuse of alcohol or drug addiction that may interfere with the subject's ability to comply with trial procedures. * Subject deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent. * Human Immunodeficiency Virus (HIV), Hepatitis B (HBs Ag) or Hepatitis C (HC) seropositivity in blood sample taken at screening. * Laboratory abnormalities considered clinically significant upon the Investigator's judgment or above the intensity thresholds (defined in the protocol) in blood sample taken at screening. * Participation in another clinical trial in the 4 weeks preceding the first trial vaccination. * Planned participation in another clinical trial during the present trial period. * Previous residence in or travel of more than 2 weeks to areas with high dengue infection endemicity. * Known systemic hypersensitivity to any of the vaccine components or history of a life-threatening reaction to the trial vaccine or a vaccine containing the same substances (i.e. egg, egg products, proteins of rodent or neural origin, gelatin, and thimerosal. * History of urticaria after hymenoptera envenomation. * History of flavivirus infection as reported by the subject. * Previous vaccination against flavivirus diseases (including Japanese encephalitis, tick-borne encephalitis, and yellow fever). * Planned travel during the present trial period to areas with high dengue infection endemicity. * 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 corticosteroid therapy (at a dose of a t least 10 mg). * Chronic illness at a stage that could interfere with trial conduct or completion. * Blood or blood-derived products received in the past 3 months. * Any vaccination in the 4 weeks preceding the first trial vaccination. * Vaccination planned in the 4 weeks following any trial vaccination. * Flavivirus vaccination planned during the present trial period.