Slizek et al.
Complications and long-term sequelae of tick-borne encephalitis: association with age and other predictors – a multicenter observational study SSRN, posted 8 January 2026
The clinical course of TBE virus infection is highly variable. Severe TBE may result in long-term sequelae. When symptoms persist for more than six months after acute infection, this is usually defined as post-encephalitis syndrome (PES).
A prospective multicenter study has been carried out in the Czech Republic between April 2023 and July 2025 to examine predictors for acute disease severity and long-term outcomes. A total of 209 patients were enrolled, and 187 completed the six-month follow-up.
Age over 50 years was significantly associated with acute severe disease, and each year of age increased the risk by about 4%. Sex was not associated with disease severity.
After six months, 84/187 patients (44.9%) reported at least one sequela, mostly fatigue (21.9%, headache (18.7%), and memory and concentration impairment (11.2%). A clear association with age was found for long-term motor deficits, which were more than three times more frequent in patients older than 50 years. However, PES was also frequent in younger patients
The severity of the acute disease was the strongest predictor of long-term outcomes. Comorbidities did not significantly influence long-term outcomes in the cohort studies in this trial.
The authors concluded that broader vaccination strategies are warranted in reducing the total health and socioeconomic impact of TBE in the Czech Republic, which is among the countries with the highest endemicity and a relatively low TBE vaccination coverage.