BACKGROUND: There are discrepant observations on severity of tick-borne encephalitis (TBE) in vaccinated patients (TBE-Vac). We, therefore, analyzed the occurrence of severe and mild disease in hospitalized vaccinated and non-vaccinated TBE patients and determined the field effectiveness (FE) of vaccination against these forms of disease. METHODS: The study covered all TBE patients hospitalized in Austria from 2000-2018. Clinical diagnoses in TBE-Vac and age- and sex-matched non-vaccinated patients were compared in a nested case-control study. FE was calculated based on vaccination coverage and incidences in the non-vaccinated and vaccinated population. RESULTS: Of 1,545 hospitalized TBE cases, 206 were TBE-Vac. In those, a higher proportion of severe TBE was observed, especially in children. FE was high in all age groups and against all forms of disease. The higher proportion of severe TBE can be explained by a lower FE against severe than against mild disease, especially pronounced in children (82.7% vs 94.7%). CONCLUSIONS: FE of TBE vaccination is excellent. The observed higher proportion of severe disease in TBE-Vac is not a consequence of higher risk associated with vaccination, but due to a somewhat lower FE against severe TBE. Since this effect was more pronounced in children, we recommend adapting the immunization schedule.
BACKGROUND: There are discrepant observations on severity of tick-borne encephalitis (TBE) in vaccinated patients (TBE-Vac). We, therefore, analyzed the occurrence of severe and mild disease in hospitalized vaccinated and non-vaccinated TBE patients and determined the field effectiveness (FE) of vaccination against these forms of disease. METHODS: The study covered all TBE patients hospitalized in Austria from 2000-2018. Clinical diagnoses in TBE-Vac and age- and sex-matched non-vaccinated patients were compared in a nested case-control study. FE was calculated based on vaccination coverage and incidences in the non-vaccinated and vaccinated population. RESULTS: Of 1,545 hospitalized TBE cases, 206 were TBE-Vac. In those, a higher proportion of severe TBE was observed, especially in children. FE was high in all age groups and against all forms of disease. The higher proportion of severe TBE can be explained by a lower FE against severe than against mild disease, especially pronounced in children (82.7% vs 94.7%). CONCLUSIONS: FE of TBE vaccination is excellent. The observed higher proportion of severe disease in TBE-Vac is not a consequence of higher risk associated with vaccination, but due to a somewhat lower FE against severe TBE. Since this effect was more pronounced in children, we recommend adapting the immunization schedule.
Authors: Michael Kunze; Pavle Banović; Petra Bogovič; Violeta Briciu; Rok Čivljak; Gerhard Dobler; Adriana Hristea; Jana Kerlik; Suvi Kuivanen; Jan Kynčl; Anne-Mette Lebech; Lars Lindquist; Iwona Paradowska-Stankiewicz; Srđan Roglić; Dita Smíšková; Franc Strle; Olli Vapalahti; Nenad Vranješ; Nataliya Vynograd; Joanna Maria Zajkowska; Andreas Pilz; Andreas Palmborg; Wilhelm Erber Journal: Microorganisms Date: 2022-06-24