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Background: A study was conducted to assess the safety and tolerability of the tetravalent live-attenuated dengue vaccine Qdenga®, which received marketing approval in Germany in 2022. The study evaluated vaccine-related reactions in a predominantly dengue-naïve population, highlighting the importance of post-marketing surveillance as an essential component of safety evaluation for newly licensed vaccines., Methods: Following dengue vaccination, participants were recruited for an anonymous online questionnaire through the national 'Trav VacNet' network in Germany. The questionnaire focused on post-vaccination reactions up to 18 days after the first and second vaccination, as well as previous travel history and coadministration., Results: The study included 1176 participants, with a median age of 39 years (IQR 28-56), 53.2% female (n = 625), 46.5% male (n = 547), and 0.3% non-binary participants (n = 4). After the first dose, 51% of the participants reported systemic reactions such as headache (40% (190/474)), weakness (40% (189/474)) and malaise (32% (154/474)), which were most pronounced between days 7-11 post vaccination. After the second dose, localized signs and symptoms such as pain at the injection site (22% (n = 55/250)) were more common. Fever was more common after the first dose (20% (96/474)) vs. 2% (6/250) after the second. Females reported significantly more reactions than males after both vaccinations (1st dose p = 0.0002; 2nd dose p = 0.0003). A total of 334 (28%) co-administrations were reported whereby AEs were reported in 47% (157/333) of participants, with the highest prevalence observed when combined with the Japanese encephalitis vaccine (56.8%, (42/74)). Differences in age groups were observed, with a decrease in reactions in the elderly (≥65 years)., Conclusions: Vaccine-related reactions were frequently reported, predominantly after the first dose in dengue-naïve participants. Coadministration was a common strategy without significantly increasing side effects. The study provides important insights into reactogenicity and may help improve vaccination strategies in dengue-naïve populations., (© International Society of Travel Medicine 2025. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)