A Study of 2 Doses of Tetravalent Dengue Vaccine (TDV) in Infants and Toddlers

Dengue fever is caused by an infection with the dengue virus. Vaccination with Dengue Tetravalent Vaccine (TDV) can help prevent dengue fever. The purpose of this study is to collect information of vaccination with TDV when given to children younger than 2 years. The main aims of this study are to learn how safe the vaccine is and how well it works to activate a young child's immune system (this is called immunogenicity). Children between the age of 6 and 21 months will receive two vaccinations with either TDV or placebo 3 months apart. Blood samples will be taken before and after the vaccination as well as throughout the study. These are necessary to check how well the vaccine works to activate the immune system. During the study, participants will visit their study clinic 8 times for vaccinations, blood draws and health checks.