Tick-Borne Encephalitis Vaccination Protects from Alimentary TBE Infection: Results from an Alimentary Outbreak

In May 2017, a hospitalized index case of tick-borne encephalitis (TBE) was confirmed by Serology. The case was linked to alimentary infection by raw milk from a goat farm in the region of Tübingen, Baden-Württemberg, Germany, where no previous TBE cases in the area had been reported before. The TBE focus was confirmed by isolation of the TBE virus from ticks and Serological confirmation of past infection in one of the five flock goats. Additional investigations by the local public health office identified 27 consumers of goat milk at the putative period of exposure. For 20/27 exposed persons, anamnestic information was gained by the local public health office. Twelve/fourteen exposed and non-vaccinated people developed clinical illness and were confirmed as TBE cases by Serology. Five/six vaccinated and exposed people did not develop the disease. The one exposed and vaccinated person had their last TBE vaccination booster more than 15 years ago, and therefore a booster was more than 10 years overdue. None of the regularly vaccinated and exposed persons developed clinical overt TBE infection. We report the first known TBE outbreak, during which, protection by TBE vaccination against alimentary TBE infection was demonstrated.