Fast-Track to Protection? A Review of Encepur's Express Dosing Schedule for Tick-Borne Encephalitis

Cases of confirmed tick-borne encephalitis (TBE) have increased dramatically over the last 30 years, highlighting growing endemicity across Eurasia. Two preventative vaccines, Encepur (Bavarian Nordic A/S, Hellerup, Denmark) and FSME-Immun (Pfizer Ireland Pharmaceuticals, Cork, Ireland), are licensed in Europe. For both vaccines, primary immunisation consists of a three-dose regimen, administered over approximately one year using "Conventional" dosing schedules. Both vaccines can also be administered using "Rapid" schedules, which shorten the interval between the first two doses but still take around a year to complete. Currently, only Encepur offers an approved "Express" schedule, whereby all three priming doses are given within 21 days. The effectiveness of TBE vaccination is markedly higher in individuals who receive ≥3 doses, compared with those who receive only one or two doses, indicating the importance of series completion. Moreover, seropositivity takes several weeks to develop after vaccination. As such, individuals are advised to initiate vaccination before peak tick season to allow sufficient time to develop protective immunity during periods of highest risk. Despite these considerations, vaccine uptake and series completion remain suboptimal in TBE-endemic regions. Furthermore, many vaccinees-including travellers with limited time before departure and residents of endemic areas-do not initiate vaccination until peak tick season, when risk is greatest. Broader use of Encepur's Express schedule may help to address these challenges. The Express schedule's 21-day timeframe may help to increase series completion by reducing drop-offs associated with prolonged dosing intervals. Additionally, it can support timely protection by enabling series completion, with sufficient time post-vaccination to develop protective immunity, all within a single-risk season, even among late initiators. In this narrative review, we evaluate the safety and immunogenicity of Encepur's Express schedule and discuss its potential utility across a broader range of vaccinees. These insights may help inform TBE vaccine recommendations and support efforts towards improving vaccination strategies amid increasing TBE risk.