Tolerability of the Dengue Vaccine TAK003 (Qdenga®) in German Travellers: Results of a Prospective Survey

Background: The global incidence of dengue has markedly increased over the last decades. Consequently, the risk for infection has increased significantly. This resulted in record numbers of imported cases in various European countries and elsewhere in 2024 and large numbers of travellers with dengue are treated in the endemic destination countries. Methods: In early 2023, TAK003, a novel, live attenuated vaccine against dengue became available in Germany. At the Berlin Centre for Travel & Tropical Medicine, we delivered 56,459 doses during the first 24 months from February 2023 until February 2025. In order to gain data on the tolerability of the vaccine in travellers, an active follow-up survey was initiated. Results: 30,306 (53.7%) vaccinees agreed to being contacted. Out of those 11,827 (39.0%) completed the anonymous questionnaire ≥4 weeks after the vaccination. Overall, 6,856 (58.0%) were female, 565 subjects (4.8%) reported to have had a prior dengue infection. The average age was 42.1 years (median 35 years, range 4-86 years). The journey to an endemic area had been completed by 6,309 subjects before answering the questionnaire and among those, 46 (0.7%) reported a dengue infection while abroad. All cases were mild, no complications were reported. TAK003 was applied with other vaccines in 7,363 (62.3%) travellers. Local adverse reactions were reported by 5,263 (47.5%) of subjects, mostly local pain. Systemic reactions were reported by 4,891 subjects (41.4%), most frequently fatigue, myalgia, and flu-like symptoms. The majority of adverse events manifested in the second week after vaccination (average 9.3 days, median 8 days) and were mostly limited to a duration of 1-3 days. A macular exanthema was described by 1,844 subjects (15.6%), typically during the second week after the vaccination. Conclusions: Side effects were frequently reported but generally well tolerated. Age groups above 50 years showed a decline of reactogenicity. Co-vaccination was frequent and led to an increase of systemic adverse events. Denominator data of the study population suggest a strong reporting bias towards adverse events. This survey adds evidence on the chronology and characteristics of adverse events associated with TAK003 and may support decision making when vaccinating dengue naïve travellers.