Tick-borne encephalitis in a child with previous history of completed primary vaccination

We report the case of a 13-year-old girl who presented with fever, headache, nausea and pain behind the right ear. Cerebrospinal fluid (CSF; leukocytes 227/L), electroencephalogram and cerebral magnetic resonance imaging were indicative of meningoencephalitis. Despite intensive therapy the general condition worsened and the patient was admitted to the intensive care unit. Serological analysis of CSF and serum indicated acute tick-borne encephalitis virus (TBEV) infection (IgG and IgM positive). TBEV infection has been reported after incomplete and complete vaccination. TBEV vaccination breakthrough in childhood has been shown to cause severe disease. It has been suggested that immunized patients develop more severe disease due to altered immune response, but the exact mechanism is unknown. In the presence of typical symptoms and a history of vaccination, possible vaccination breakthrough or missing booster vaccination should be considered.