A Study of Dengue Vaccine in Healthy Toddlers Aged 12 to 15 Months in the Philippines

Participants will be enrolled in a 3-step enrollment and randomized to 1 of 4 treatment groups. Groups 1 and 2 will receive 5 vaccinations, and Groups 3 and 4 will received 6 vaccinations (childhood vaccines or placebo co-administered with the first dose of CYD Dengue vaccine in 2 separate arms). All toddlers will receive a pentavalent acellular pertussis combination vaccine or Combo (PENTAXIM®), planned approximately 10 months after enrollment.

Inclusion criteria

• Toddler in good health based on medical history and medical examination
• Toddler aged 12 to 15 months on the day of inclusion
• Born at full term of pregnancy (≥ 37 weeks) and with a birth weight ≥ 2.5 kg
• Provision of informed consent form signed by the parent(s) or other legally acceptable representative (and by an independent witness if required by local regulations)
• Participant and parent/delegate able to attend all scheduled visits and comply with all trial procedures
• Completion of previous vaccination program according to the national immunization schedule, except for measles

Exclusion criteria

• Family members from the Investigator or from the staff involved in the trial
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion
• Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term systemic corticosteroids therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months)
• History of central nervous system disorder or disease, including seizures
• History of varicella, measles, mumps, rubella and hepatitis A; confirmed either clinically, serologically, or microbiologically
• Thrombocytopenia, bleeding disorder or anticoagulants in the 3 weeks preceding inclusion
• Previous vaccination against measles-mumps-rubella, hepatitis A or varicella
• Previous vaccination against flavivirus diseases
• Known systemic hypersensitivity to any of the components of the vaccines, or history of a life-threatening reaction to the vaccines used in the trial or to a vaccine containing any of the same substances
• Planned participation in another clinical trial during the present trial period
• Participation in another clinical trial investigating a vaccine, drug, medical device, or medical procedure in the 4 weeks preceding the first trial vaccination
• Receipt of blood or blood-derived products in the past 3 months, which might interfere with assessment of the immune response
• Planned receipt of any vaccine in the 4 weeks following the first trial vaccination
• Human immunodeficiency virus (HIV) seropositivity in the blood sample taken at screening
• Clinically significant laboratory abnormalities, as judged by the Investigator, in blood sample taken at screening

Temporary exclusions: vaccination postponed until the condition is resolved:

• Febrile illness (temperature ≥ 38°C) or moderate or severe acute illness/infection on the day of vaccination, according to Investigator judgment
• Receipt of oral or injected antibiotic therapy within 72 hours prior to the vaccination visit
• Any vaccination received in the 4 weeks preceding vaccination