Long-term persistence of tick-borne encephalitis antibodies in adults 5 years after booster vaccination with Encepur Adults.

Tick-borne encephalitis (TBE) is a potentially serious disease, especially in adults. There is no treatment available for TBE; supportive therapy may help to ease symptoms of the disease. Vaccination is the most effective method of preventing TBE disease and is recommended for those who live, work, or travel in TBE-endemic areas. Regular booster vaccinations are recommended every 3-5 years to maintain protection. Evidence from recent clinical studies suggests that TBE antibodies persist at high levels for longer than the current recommended intervals for TBE booster vaccination. The aim of this study was to evaluate the long-term persistence of TBE antibodies in adults after primary vaccination using a rapid schedule and a first booster dose of Encepur Adults, an inactivated TBE vaccine. A total of 222 adults 19-51 years of age were invited for serological follow-up investigations 3 and 5 years following their first booster dose. High antibody titres were recorded throughout the follow-up period. Neutralization test (NT) titres > or =10 were noted in 99% of subjects 3 and 5 years after the first booster vaccination and 97% tested positive by enzyme-linked immunosorbent assay (ELISA). These results indicate that initially high levels of TBE antibodies following the first booster dose of the vaccine may lead to long-term persistence of TBE antibodies, confirming previous findings and suggesting it may be appropriate to extend the interval between booster doses from 3 to 5 years.