TDENV PIV and LAV Dengue Prime-boost Strategy Using AS03B Adjuvant

Inclusion Criteria: * Subjects who in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g., document events in memory aid, return for follow-up visits, etc.) * Between 18 and 39 years of age (inclusive) at the time of consent * Written informed consent obtained from the subject * Healthy subjects as established by medical history and clinical examination before entering into the study. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study vaccines/placebo during the period starting 30 days preceding the first dose of study vaccine/placebo and/or planned use during the study period * Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immune-modifying drugs during the period starting 180 days prior to the first vaccine/placebo dose (for corticosteroids, this will mean prednisone 20 mg/day or equivalent; inhaled and topical steroids are allowed) * Planned administration or administration of a vaccine/product not foreseen by the study protocol during the period starting 30 days before or after each scheduled dose of an investigational product or placebo. * Planned administration of any flavivirus vaccine for the entire study duration * Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or an approved/cleared non-investigational product (pharmaceutical product or device). * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required). * Family history of congenital or hereditary immunodeficiency * History and family history of a bleeding disorder * History of past flavivirus infection or vaccination (Yellow Fever, tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV), West Nile virus (WNV), dengue (DENV) * History of, or current, auto-immune disease * History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine/placebo or related to a study procedure * Major congenital defects or serious chronic illness * History of any neurological disorders or seizures * Acute disease and/or fever (≥ 100.4° ◦F / 38.0° ◦C, oral body temperature) at the time of enrollment (a subject with a minor illness, i.e., mild diarrhea, mild upper respiratory infection, etc., without fever, may be enrolled at the discretion of the investigator) * Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic, or renal functional abnormality, as determined by physical examination or laboratory screening tests * Administration of immunoglobulins and/or any blood products during the period starting 90 days preceding the first dose of study vaccine/placebo or planned administration during the study period * History of chronic alcohol consumption and/or drug abuse * A planned move to a location that will prohibit participating in the trial until study end for the participant * Any other condition which, in the opinion of the investigator, prevents the subject from participating in the study. * Subject seropositive for hepatitis B surface antigen (HBsAg), hepatitis C virus antibodies (anti-HCV), or human immunodeficiency virus antibodies (anti-HIV) * Safety laboratory test results that are outside the acceptable values at screening.