Biswal S, Borja-Tabora C, Vargas LM, et al. - Researchers conducted this randomised, placebo-controlled, phase 3 trial to test the effectiveness, safety, and immunogenicity of a live attenuated tetravalent dengue vaccine (TAK-003) in healthy children aged 4–16 years. Data from an ongoing phase 3, randomised, double-blind trial of TAK-003 in endemic regions of Asia and Latin America (26 medical and research centres across Brazil, Colombia, Dominican Republic, Nicaragua, Panama, Philippines, Sri Lanka, and Thailand) up to 18 months after vaccination are presented. Healthy children (aged 4 to 16 years) have been randomly assigned 2:1 (stratified by age and region) to receive two doses of TAK-003 or two doses of placebo, 3 months apart. Twenty thousand ninety-nine participants were randomly assigned and vaccinated between September 7, 2016, and August 18, 2017; 19,021 (94·6%) were included in the per protocol analysis, and 20,071 (99·9%) in the safety set. Before immunisation, TAK-003 was well tolerated and efficacious against symptomatic dengue in children independent of serostatus. Vaccine efficacy varied by serotype, ensuring ongoing follow-up to determine vaccine effectiveness in the longer term.