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In Europe, dengue primarily is imported from endemic countries. However, an increasing number of autochthonous cases and limited outbreaks have been described since 2010. In 2023, a total of 105 [...]

BACKGROUND. Disease due to dengue viruses is a growing global health threat, causing 100-400 million cases annually. An ideal dengue vaccine should demonstrate durable protection against all 4 serotypes in phase III efficacy trials, however the lack of circulating serotypes may lead to incomplete efficacy data. Controlled human infection models help downselect vaccine candidates and supply critical data to supplement efficacy trials. We evaluated the efficacy of a leading live-attenuated tetravalent dengue vaccine candidate, TV005, against infection with a newly established dengue serotype 3 or an established serotype 2 challenge virus. METHODS. Two randomized, controlled clinical trials were performed. In study 1, a total of 42 participants received TV005 or placebo (n = 21 each), and 6 months later, all were challenged with dengue 2 virus (rDEN2[DELTA]30) at a dose of 103 PFU. In study 2, a total of 23 participants received TV005 and 20 received placebo, and 6 months later, all were challenged with 104 PFU dengue 3 virus (rDEN3[DELTA]30). The study participants were closely monitored for safety, viremia, and immunologic responses. Infection, measured by post-challenge viremia, and the occurrence of rash and neutropenia were the primary endpoints. Secondary endpoints included safety, immunologic, and virologic profiles following vaccination with TV005 and subsequent challenge with the rDEN2[DELTA]30 or rDEN3[DELTA]30 strain. RESULTS. TV005 was well tolerated and protected all vaccinated volunteers from viremia with DENV2 or DENV3 (none infected in either group). Placebo recipients had post-challenge viremia (100% in study 1, 85% in study 2), and all experienced rash following challenge with either serotype. CONCLUSIONS. TV005 is a leading tetravalent dengue vaccine candidate that fully protected against infection with DENV2 and DENV3 in an established controlled human infection model. TRIAL REGISTRATION. ClinicalTrials.gov NCT02317900 and NCT02873260. FUNDING. Intramural Research Program, NIH (contract HHSN272200900010C)., Introduction Dengue viruses are estimated to cause 100-400 million symptomatic illnesses each year, with a significant and expanding burden of severe disease and mortality in both endemic populations and travelers [...]