"Borreliosis" or "Lyme disease" is caused by the bacterium "Borrelia burgdorferi". In Austria approximately 16,000 people fall ill with borreliosis annually following a tick bite. Roughly every fifth tick in Austria carries the pathogen. Borreliosis can be treated effectively with antibiotics, however a prophylactic vaccination is not available. In a current multicentre study, in which the MedUni Vienna participated, the reliable effectiveness of a possible vaccine against borreliosis has now been proved.