Efficacy and Safety of a Tetravalent Dengue Vaccine (TAK-003) in Children With Prior Japanese Encephalitis or Yellow Fever Vaccination.

backgroundWe explored the impact of prior yellow fever (YF) or Japanese encephalitis (JE) vaccination on the efficacy of Takeda's dengue vaccine candidate, TAK-003.

methodsChildren 4-16 years of age were randomized 2:1 to receive TAK-003 or placebo and were under active febrile surveillance. Symptomatic dengue was confirmed by serotype-specific reverse-transcription polymerase chain reaction. YF and JE vaccination history was recorded.

resultsOf the 20 071 children who received TAK-003 or placebo, 21.1% had a YF and 23.9% had a JE vaccination history at randomization. Fifty-seven months after vaccination, vaccine efficacy (95% confidence interval) was 55.7% (39.7%-67.5%) in those with YF vaccination, 77.8% (70.8%-83.1%) for JE vaccination, and 53.5% (45.4%-60.4%) for no prior YF/JE vaccination. Regional differences in serotype distribution confound these results. The apparent higher vaccine efficacy in the JE vaccination subgroup could be largely explained by serotype-specific efficacy of TAK-003. Within 28 days of any vaccination, the proportions of participants with serious adverse events in the YF/JE prior vaccination population were comparable between the TAK-003 and placebo groups.

conclusionsThe available data do not suggest a clinically relevant impact of prior JE or YF vaccination on TAK-003 performance. Overall, TAK-003 was well-tolerated and efficacious in different epidemiological settings. Clinical Trials Registration.  NCT02747927.