Complications and long-term sequelae of tick-borne encephalitis: association with age and other predictors - a multicenter observational study.

Tick-borne encephalitis (TBE) is the most common non-purulent neuroinfection in Central Europe and a major public health concern in the Czech Republic, where vaccination coverage remains low. Even after recovery from the acute disease, many patients experience long-term sequelae known as postencephalitic syndrome (PES). This prospective multicentre study examined predictors of acute disease severity and long-term outcomes, including motor deficits and other forms of PES. A total of 209 patients with laboratory-confirmed TBE were enrolled at four Czech centres in 2023 and 2024; 187 completed six-month follow-up. Logistic regression models were used to evaluate the associations between patient characteristics, acute disease severity, and outcomes. Age over 50 years was significantly associated with a severe acute course (OR = 2.70, 95 % CI 1.44-5.07). After six months, 84 of 187 patients (44.9 %) reported at least one sequela. PES affected patients across all age groups, while age showed only a non-significant trend toward higher PES frequency and severity. Persistent motor deficits occurred in 23 patients (12.3 %) and were linked to older age (OR = 3.73, 95 % CI 1.34-10.4, p < 0.05); female sex was associated with lower risk (OR = 0.31, 95 % CI 0.11-0.92, p < 0.05). Comorbidities showed no independent association. These findings indicate that while acute-phase severity contributes to adverse outcomes, PES can develop regardless of age or disease severity and only motor deficits are strongly age-associated. The results underscore the need for vaccination across all age groups in endemic regions.