A Phase II Trial of a Live Attenuated Virus Tetravalent Dengue Vaccine in Healthy Adults in Thailand

Inclusion Criteria: * A healthy male or female adult 20-25 years of age (≥20 years of age and ≤25 years of age) at the time of vaccination; * Free of obvious health problems as established by medical history and physical examination before entering into the study; * Written informed consent obtained from the subject; * Able to read the Subject Information Sheet and Consent Form; * Subjects who the investigator believes can and will comply with the requirements of the protocol (e.g., completion of the diary cards, return for follow-up visits) should be enrolled in the study; * females must be of non-childbearing potential, i.e. surgically sterilized or, if of childbearing potential, she must be abstinent or on adequate contraceptive precautions (i.e. intrauterine contraceptive device; oral contraceptives or other equivalent hormonal contraception, e.g. progestin implantable, cutaneous hormonal patch or injectable contraceptives) for 30 days prior to vaccination, have a negative pregnancy test within 48 hours prior to vaccination and must agree to continue such precautions for 60 days after completion of the vaccination series Exclusion Criteria: * Pregnant or lactating female, planning to become pregnant or planning to discontinue abstinence or contraceptive precautions; * History of any neurological or behavioral disorder or seizures, with the exception of a single febrile seizure in childhood; * History of drug abuse or alcohol consumption (more than 2 drinks per day); * History of allergic disease/reaction likely to be exacerbated by any component of the vaccine; * Acute or chronic, pulmonary, cardiovascular, hepatic, renal, hematologic or endocrine functional defect, as determined by physical examination or laboratory tests; * Any confirmed or suspected immunosuppressive or immunodeficient condition or seropositive for HBsAg, anti-HCV or anti-HIV; * Acute disease at the time of enrollment (acute disease is defined as the presence of a moderate or severe illness with or without fever); * Chronic hepatomegaly, right upper quadrant abdominal pain or tenderness; * Chronic splenomegaly, left upper quadrant abdominal pain or tenderness; * Hypertension; chest pain, palpitations, dizziness, shortness of breath, arrhythmias or friction rubs; * Use of any investigational or non-registered drug or vaccine other than the study vaccine within 30 days preceding the study vaccine (includes placebo) or planned use during the study period; * Planned administration of a vaccine not foreseen by the study protocol during the period starting from 30 days before the first dose of the study vaccine/placebo and ending 30 days after the second dose; * A planned move to a location that will prohibit participating in the trial for 9 months after the initial vaccination; * Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within 90 days preceding the first dose or planned administration during the study period. For corticosteroids, this will mean prednisone, or equivalent, 0.5 mg/kg/day. Inhaled and topical steroids are allowed; * Administration of immunoglobulins and/or blood products within 90 days preceding the first dose or planned administration during the study period; * Any chronic systemic drug therapy to be continued during the study period (except for vitamin/mineral supplements or routine treatment for gastro-esophageal reflux); * No easy access to a fixed or mobile telephone