Measles, first described in the 10th century, is a viral infectious disease, which is spread by droplets. Humans are the only reservoir of the virus. Widespread epidemics caused a great number of deaths in the Middle Ages, and not without cause measles has been called the greatest killer of children in history. According to the World Health Organization, even in 2003 about 500 000 people, mostly children, died from measles. After an incubation period of 10–14 days the prodromal stage appears, which is characterized by fever and inflammatory reactions of the respiratory tract and the eyes. One can speak of the typical three Cs, which are cough , coryza (running nose) and conjunctivitis (red eyes). The second stage of the infection starts after 12–13 days with a reddening of the palate and the mucous membrane of the cheeks. Two to three days later the typical maculopapular rash delvelops, starting behind the ears and then spreading over the whole body. Possible complications are a swelling of the larynx (croup), pneumonia, corneal and retinal damage and inflammation of the brain (encephalomyelitis). A rare, but extremely feared complication is subacute sclerosing panencephalits (SSPE) . SSPE is an inflammation of the whole brain, which appears months or years after infection with measles. The disease, which cannot be treated, is progressive and always leads to death. The most important measure to prevent an infection with measles is the active measles‐vaccination (immunization, active).