Sociological interest in vaccination has recently increased, largely in response to media coverage of concerns over the safety of the MMR (measles, mumps and rubella) vaccine. The resulting body of research highlights the importance of risk and trust in understanding parental and professional engagement with vaccination. To date, only limited attention has been paid to organised parental groups that campaign against aspects of vaccination policy. This paper reports findings from a qualitative study of contemporary groups in the UK, and develops three main lines of argument. First, these actors are best analysed as 'Vaccine Critical groups' and include Radical and Reformist types. Second, Vaccine Critical groups discursively resist vaccination through a reframing that constructs risk as unknown and non-random. Third, trust as faith is negatively contrasted with the empowerment that is promised to result from taking personal responsibility for health and decision-making. Whilst representing a challenge to aspects of vaccination policy, this study confirms that the groups are involved in the articulation and promotion of other dominant discourses. These findings have implications for wider sociological debates about risk and trust in relation to health.