The purpose of this study is to generate immunogenicity and safety data in preparation for efficacy studies in Latin America.

Primary Objectives:

• To describe the immune response to dengue viruses before and after each vaccination with CYD dengue vaccine.
• To evaluate the safety of each vaccination with CYD dengue vaccine.

Participants in the Dengue Vaccine Group will receive 3 vaccinations with CYD Dengue vaccine. Participants in the Control Group will receive placebo vaccinations for the first 2 vaccinations, followed by tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine adsorbed (ADACEL®) (in Venezuela) or Meningococcal A+C vaccine (in Brazil) as a way of providing therapeutic benefit to the participants in the control group.

Inclusion Criteria :

• Aged 9 to 16 years on the day of inclusion
• Participant in good health, based on medical history and physical examination
• Provision of assent form/informed consent form signed by the participant and by the parent(s) or another legally acceptable representative
• Participant and parent(s)/legally acceptable representative(s) able to attend all scheduled visits and to comply with all trial procedures
• For a female participant of child-bearing potential, avoid becoming pregnant (use of an effective method of contraception or abstinence) for at least 4 weeks prior to first vaccination until at least 4 weeks after the last vaccination

Exclusion Criteria :

• Personal or family history of thymic pathology (thymoma), thymectomy, or myasthenia
• For a female participant of child-bearing potential, known pregnancy or positive urine pregnancy test at Visit 1
• Participation in another clinical trial investigating a vaccine, drug, medical device, or a medical procedure in the 4 weeks preceding the first trial vaccination
• Breast-feeding woman
• 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 systemic corticosteroids therapy
• Known systemic hypersensitivity to any of the components of any of the trial vaccines or history of a life-threatening reaction to any of the trial vaccines 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 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 preceding 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 the first trial vaccination
• Participant deprived of freedom by administrative or court order, or in an emergency setting, or hospitalized without his/her consent
• Febrile illness (temperature ≥ 38.0 ºC) or moderate or severe acute illness/infection on the day of vaccination, according to Investigator judgment
• Thrombocytopenia, bleeding disorder or anticoagulants in the 3 weeks preceding inclusion contraindicating intramuscular vaccination
• Severe diseases with or without fever, convulsions or neurological abnormalities without treatment or in progression.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org