A phase 3 clinical trial evaluated the efficacy and safety of a tetravalent dengue vaccine (CYD-TDV) in healthy children aged 9 to 16 years in five Latin American countries. The vaccine, which is a recombinant, live-attenuated dengue vaccine, was tested against symptomatic, virologically confirmed dengue (VCD) in a randomized, blinded, placebo-controlled trial. A total of 20,869 children received either the vaccine or placebo. The primary outcome was vaccine efficacy against VCD, regardless of disease severity or serotype, occurring more than 28 days after the third injection. The vaccine showed 60.8% efficacy against VCD in the per-protocol population and 64.7% efficacy in the intention-to-treat population. Serotype-specific efficacy was 50.3% for serotype 1, 42.3% for serotype 2, 74.0% for serotype 3, and 77.7% for serotype 4. The vaccine was also effective against severe VCD, with an efficacy of 95.5% in the intention-to-treat population. Vaccine efficacy against hospitalization for dengue was 80.3%. The safety profile of the vaccine was similar to that of the placebo, with no marked difference in the rates of adverse events. The study found that the CYD-TDV vaccine was efficacious against VCD and severe VCD and led to fewer hospitalizations for VCD in five Latin American countries where dengue is endemic. The vaccine was well tolerated, with no serious adverse events reported. The study was funded by Sanofi Pasteur and conducted in accordance with ethical and regulatory guidelines. The results of this trial are consistent with those of a similar trial in Asia, where the vaccine showed similar efficacy against all four dengue serotypes. The study highlights the importance of large, multicenter trials to evaluate the efficacy of dengue vaccines in diverse epidemiologic settings. The vaccine's safety profile was consistent with previous reports, and no major safety concerns were identified. The study also found that the vaccine was effective in children with a seropositive status at baseline, with higher efficacy compared to those with a seronegative status. The results of this trial provide important insights into the efficacy and safety of the CYD-TDV vaccine in children in Latin America.A phase 3 clinical trial evaluated the efficacy and safety of a tetravalent dengue vaccine (CYD-TDV) in healthy children aged 9 to 16 years in five Latin American countries. The vaccine, which is a recombinant, live-attenuated dengue vaccine, was tested against symptomatic, virologically confirmed dengue (VCD) in a randomized, blinded, placebo-controlled trial. A total of 20,869 children received either the vaccine or placebo. The primary outcome was vaccine efficacy against VCD, regardless of disease severity or serotype, occurring more than 28 days after the third injection. The vaccine showed 60.8% efficacy against VCD in the per-protocol population and 64.7% efficacy in the intention-to-treat population. Serotype-specific efficacy was 50.3% for serotype 1, 42.3% for serotype 2, 74.0% for serotype 3, and 77.7% for serotype 4. The vaccine was also effective against severe VCD, with an efficacy of 95.5% in the intention-to-treat population. Vaccine efficacy against hospitalization for dengue was 80.3%. The safety profile of the vaccine was similar to that of the placebo, with no marked difference in the rates of adverse events. The study found that the CYD-TDV vaccine was efficacious against VCD and severe VCD and led to fewer hospitalizations for VCD in five Latin American countries where dengue is endemic. The vaccine was well tolerated, with no serious adverse events reported. The study was funded by Sanofi Pasteur and conducted in accordance with ethical and regulatory guidelines. The results of this trial are consistent with those of a similar trial in Asia, where the vaccine showed similar efficacy against all four dengue serotypes. The study highlights the importance of large, multicenter trials to evaluate the efficacy of dengue vaccines in diverse epidemiologic settings. The vaccine's safety profile was consistent with previous reports, and no major safety concerns were identified. The study also found that the vaccine was effective in children with a seropositive status at baseline, with higher efficacy compared to those with a seronegative status. The results of this trial provide important insights into the efficacy and safety of the CYD-TDV vaccine in children in Latin America.