Seropersistence of TBE virus antibodies 10 years after first booster vaccination and response to a second booster vaccination with FSME-IMMUN 0.5mL in adults.

Tick-borne encephalitis (TBE) is a viral disease that can have a severe acute clinical course and considerable long-term morbidity. As there is no causal treatment currently available for TBE, vaccination is the only way to combat the disease in endemic areas. The studies presented here were conducted to obtain prospective long-term TBE serum antibody persistence data of subjects up to 10years after the first booster with FSME-IMMUN. This report presents the results of 2 follow-up studies in the same study population of 315 healthy adults. Blood was drawn to assess the seropersistence of TBE virus antibodies yearly, from 2-5 and 7-10years after the first booster vaccination with FSME-IMMUN administered during a previous study. The timing of the second booster vaccination was dependent on the level of serum TBE antibodies observed during yearly follow-up serology observations. The current follow up showed that adult recipients were 84.9% seropositive 10years after a 3 dose primary series and the first booster vaccination of FSME-IMMUN. Seropositivity rates were even higher (88.6%) in subjects below 50years of age. ClinicalTrials.gov Identifier: NCT00503529. ClinicalTrials.gov Identifier: NCT01582698.