The long-term efficacy of tick-borne encephalitis vaccines available in Europe as part of conventional immunization schedules. A systematic review. Running title: Long-term efficacy of tick-borne encephalitis vaccines

Abstract Background To assess the long-term efficacy of vaccinations against tick-borne encephalitis using vaccines available on the European market. Methods The analysis was conducted on the results of a systematic review conducted in accordance with the Cochrane Collaboration guidelines. The search was performed in three databases, namely Medline (via PubMed), EMBASE (via Ovid), and the Cochrane Library database. Results From a total of 199 citations, 9 studies were included in this review. According to the primary studies identified in the search, the efficacy of available anti-TBE vaccines ranges from 90.1–98.9%; however, in individuals above the age of 60, the protection wanes as early as one year after vaccination. Administration of a booster dose 3 years after completion of the basic vaccination schedule significantly extends the period of protection against TBE. Conclusions Anti-TBE vaccines available in Europe have a high level of efficacy; however, one should bear in mind that the level of protection against TBE is steadily decreasing after vaccination. Following the basic vaccination according to the conventional schedule, booster vaccines should be administered every 5 years in individuals before the age of 60 and more frequently, e.g. every 3 years, in individuals aged 60 and beyond.