Tick-borne encephalitis after vaccination: vaccine failure or misdiagnosis.

The aim of the paper is to present the results of the investigation of a series of four cases of tick-borne encephalitis (TBE) reported from Gorenjska region in Slovenia in 2008 despite vaccination against TBE, propose surveillance case definition for TBE and classification criteria for TBE vaccine failure cases, to discuss challenges in the interpretation of TBE serology results in previously vaccinated patients and propose ascertainment procedures for vaccine failure cases. Establishing surveillance of vaccine failure cases on national and European level is essential for monitoring and evaluating the impact of immunization, evaluation of vaccine effectiveness and early warning for the need to change the vaccination schedule recommendations.