[Reactions after MMR vaccination].

Four months after introducing routine vaccination against measles, mumps and German measles (MMR-vaccination) in Denmark, a questionnaire study of reactions in vaccinated children was carried out. There were significantly fewer reactions in children who had previously developed immunity to measles, either by having had the disease or by vaccination. The reaction frequency after MMR-vaccination of children immune to measles was no greater than that after other vaccinations. Moreover, for all vaccinations, the frequency of reaction was found to decrease significantly with increasing age. The study suggests that a large proportion of the so-called reactions were not caused by vaccination, but were due to common viral infections occurring at random and concurrently with it. The reactions that arose in connection with MMR-vaccination are considered to be of minor importance when compared with often prolonged and more severe course of these diseases.