**6.4. TBE in patients who had been vaccinated against the disease**

It seems that breakthrough TBE after vaccination is rare: 7 cases were reported in Slovenia, 25 in Austria, and 27 in Sweden in the periods 2000–2006, 2000–2008, and 2002–2008, respectively. The majority (70%) of patients were over 50 years old, but also a pediatric case has been described [63–67]. According to Kunz, disease severity in unvaccinated and vaccinated patients with TBE does not differ substantially; however, the information is limited [68].

#### **6.5. Chronic progressive TBE**

A chronic progressive form of TBE, believed to be associated with the Siberian subtype of TBEV, has been described in Siberia and Far East. It may manifest with *epilepsia partialis continua* [69–72].

#### **6.6. Postencephalitic syndrome**

According to published data postencephalitic syndrome occurs in up to 58% of patients after acute TBE caused by European subtype of TBEV, and may include various nonspecific neurological/neuropsychiatric symptoms and residual neurological dysfunctions [73]. It often affects the patient's quality of life (sometimes requires a change in lifestyle) and also represents a high cost for the health care system and society.

The most commonly reported symptoms/signs have been cognitive or neuropsychiatric complaints (i.e., apathy, irritability, memory and concentration disorders, altered sleep pattern), headache, hearing defects, disturbances of vision, ataxia, and pareses or flaccid paralyses [46, 47, 58, 73, 74]. At this point it should be noted that most of the studies failed to include a control group; therefore, the findings are difficult to interpret due to unclear differences between postencephalitis syndrome, other consequences of TBE and symptoms present in the general population.

Lithuanian prospective clinical follow‐up study showed that 46% of patients with TBE had sequelae 1 year post infection [47]. In 2009, Misić‐Majerus et al. published a prospective study on TBE postencephalitic syndrome. One hundred and twenty‐four patients, aged 16–76 years, participated in the study with follow‐up period for at least 3 years. Forty‐nine patients (39.5%) developed moderate or severe sequelae lasting for 3 to 18 months; in 11 patients permanent sequelae were seen—spinal nerve paresis in five, hearing impairment in six, dysarthria in two, and severe mental disorder in one patient [74]. In 2011, Kaiser reported 10‐year follow‐up results in patients with encephalomyelitic manifestation of TBE; 11 (19%) out of 57 included patients fully recovered, 29 (51%) patients had long‐lasting sequelae (paresis or other impairments), and 17 (30%) died 1–10 years after the acute disease. The most substantial improvements were seen in the first year after acute disease [75]. Recently published case‐control study on the long-term sequelae after TBE from Sweden has showed that the neurocognitive and motor symptoms in patients significantly differ from those in the age‐ and gender‐ matched control group [76].
