Tick-borne encephalitis in international travellers: a systematic review and vaccine recommendations

Background: Tick-borne encephalitis (TBE) is a potentially life-threatening infectious disease caused by the tick-borne encephalitis virus (TBEV). In recent years, TBE-endemic areas have expanded in Europe and the incidence of surveillance-reported TBE cases has increased. TBE is preventable through vaccination, with vaccines available and recommended for residents of, and travellers to, TBE-endemic regions. We summarized the published literature on international travel-associated TBE cases and country-specific TBE vaccine recommendations for travellers. Methods: We conducted a systematic literature review using PubMed and Web of Science and reviewed public health surveillance online sources to identify reports of travel-associated TBE cases published from 1978 to 2024. We also analysed the European Centre for Disease Prevention and Control (ECDC) TBE Annual Epidemiological Reports from 2015 to 2022 for travel-associated cases and collected information on TBE vaccination recommendations by national public health authorities for travellers to Europe. Results: Thirty-nine international travel-associated TBE cases were identified from 24 articles and one public health report. Of the 34 travel-associated TBE cases with clinical information, 33 (97.0%) were hospitalized for a median of 9 days. Travel-associated cases departed from the USA, Israel and several countries in Europe; the most frequently visited countries were Austria, Russia, Sweden and Switzerland. Of the 22 191 surveillance-reported TBE cases reported to ECDC from 2015 to 2022, 376 (1.7%) were international travel-associated cases. Recommendations for TBE vaccination for travellers were identified in 32 countries. Conclusions: Despite recommendations for TBE vaccination for travellers to TBE-endemic areas in Europe, international travel-associated TBE cases among travellers to Europe continue to occur. Most of the published travel-associated TBE cases are associated with severe clinical illness. When considering the increasing geographic spread of the TBE-endemic areas and increasing TBE incidence in Europe, enhanced efforts are needed to inform appropriate international travellers about the risk of TBE and to promote vaccination of travellers to TBE-endemic areas in Europe.