This paper examines the controversy over measles, mumps and rubella (MMR) vaccine in Britain through the lenses of social movement theory and social studies of science. Since the early 1990s, networks of parents have raised, and mobilised around, concerns that MMR has triggered a particular disease in their children linked to autism and bowel problems, and have been supported in this by certain scientists. In the high-profile and highly-public debate which has ensued, they have challenged established perspectives and institutions in both biomedical science, and public health policy. While much policy and public debate has dismissed their concerns as based on emotion, misinformation or “junk science”, this paper locates them as part of a citizen science grounded in parental experience.

It tracks how the framing and strategies of parental mobilisation around MMR have developed, in relation to a growing counter-mobilisation from scientists, policy-makers, health professionals and journalists questioning their claims. It argues that the controversy involves differently-framed sciences (clinical vs epidemiological) linked to different political commitments (parents’ personal concerns and rights as citizen-consumers vs notions of public health). Each side has nevertheless used similar strategies in deploying science, in exposing the political economy of the other’s science, and in working through the media. Both these differences of framing, and similarities of strategy, are important to comprehending why the debate has become so heated and polarised, and why it has failed to reach closure. Keywords: citizens, science, mobilisation, vaccination, MMR