Healthy adolescents and adults who received 3 doses of the tetravalent dengue vaccine 5 years earlier in a previous CYD dengue vaccine trial (CYD28 - NCT00880893) will receive a booster injection of either a CYD dengue vaccine or a placebo on Day 0. They will be evaluated for safety and antibody persistence of the booster injection up to 2 years post-vaccination.