Tricou V, Sáez-Llorens X, Yu D, et al. - Researchers here evaluated three different dose schedules of a tetravalent dengue vaccine (TAK-003) over a 48-month period for the immunogenicity and safety in children living in dengue-endemic countries. A large, phase 2, double-blind, placebo-controlled trial including healthy participants aged 2–17 years was conducted at three sites in the Dominican Republic, Panama, and the Philippines. From Dec 5, 2014, to Feb 13, 2015, they randomly assigned 1,800 children to the following groups: two-dose primary series (days 1 and 91; n = 201), one primary dose ( day 1; n = 398), one primary dose plus 1-year booster (days 1 and 365; n = 1,002), and placebo (n = 199). Outcomes revealed elicitation of antibody responses against all four serotypes following administration of TAK-003; these responses persisted to 48 months postvaccination, regardless of baseline serostatus. They identified no important safety risks. Vaccinees exhibited a long-term reduction in risk of symptomatic dengue virus disease. This study yields a long-term safety database and support evaluation of the vaccine in the ongoing phase 3 efficacy study.