The vaccine tested in this study is Takeda's Tetravalent Dengue Vaccine Candidate (TDV). This study will look at the long-term antibody persistence and safety of Takeda's TDV in healthy adolescents and adults and will assess the impact of a booster dose.

The study has enrolled 365 healthy participants. Participants who previously received TDV in two parent trials (DEN-304 [NCT03423173] and DEN-315 [NCT03341637]), will be invited to participate in this follow-up trial. Participants will be assessed for antibody persistence and safety from Baseline (Month 0) through Month 15. At Month 15, eligible participants will be randomized in 1:1 ratio to one of two trial groups to receive TDV or placebo:

Group 1- TDV 0.5 mL subcutaneous (SC) injection at Month 15 Group 2- Takeda's tetravalent dengue placebo (dummy SC injection - this is a liquid that looks like the study drug but has no active ingredient), 0.5 mL, subcutaneous injection at Month 15

This multi-centre trial will be conducted in United States and Mexico. The overall time to participate in this study is up to 21 months. Participants will make 7 visits to the clinic including a final visit 6 months after last dose of study drug for a follow-up assessment.