Immunogenicity and Safety of Three Formulations of Dengue Vaccines in Healthy Adults Aged 18 to 45 Years in the US

Inclusion Criteria: * Healthy, as determined by medical history, clinical examination, and biological safety parameters. * Aged 18 to 45 years on the day of inclusion. * Provision of informed consent signed by the participant or another legally acceptable representative. * 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 until at least 4 weeks after the last study vaccination. * Able to attend all scheduled visits and to comply with all trial procedures. Exclusion Criteria: * Personal or family history of thymic pathology (thymoma), thymectomy, or myasthenia. * For a woman of child-bearing potential, known or suspected pregnancy or positive serum/urine pregnancy test. * Breast-feeding woman. * Participation in another clinical trial investigating a vaccine, drug, medical device, or a medical procedure in the 4 weeks preceding the first trial vaccination. * Planned participation in another clinical trial during the present trial period. * 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). Topical steroids were allowed. * Known systemic hypersensitivity to any of the vaccine components or history of a life-threatening reaction to the trial vaccine or to a vaccine containing any of the same substances. * Chronic illness at a stage that could interfere with trial conduct or completion, in the opinion of the investigator. * Current or past alcohol abuse or drug addiction that may interfere with the participant's ability to comply with trial procedures. * Receipt of blood or blood-derived products in the past 3 months, that might interfere with the assessment of immune response. * Receipt of any vaccine in the 4 weeks preceding the first trial vaccination. * Planned receipt of any vaccine in the 4 weeks following each of the trial vaccinations. * Human Immunodeficiency Virus (HIV), hepatitis B surface antigen, or hepatitis C virus seropositivity in blood sample taken at Screening. * Participant deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent. * Clinically significant laboratory test abnormalities (as determined by the investigator) in blood sample taken at Screening. * Previous residence in, travel or planned travel of more than 2 weeks during the study period to areas with high dengue infection endemicity. * Reported history of flavivirus infection as reported by the participant. * Previous vaccination against flavivirus diseases (including Japanese encephalitis, tick-borne encephalitis, and yellow fever). * Flavivirus vaccination planned during the trial period.