A decade ago, the possibility of a link between the MMR vaccine and autism hit the media. Fear of the vaccine spread rapidly and, despite an almost unanimous consensus that the claim was unfounded, still persists today. In this unit, we’ll examine why this controversy took on such a life of its own and why parents still agonise about the vaccine. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.