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.