Recent data and increased vaccine-preventable disease outbreaks suggest that a growing number of US parents choose not to vaccinate their children. Popular media have responded to this phenomenon by emphasizing refusers’ moral failings and irrational fears. This article explores vaccine skeptics’ objections and argues that their critics miss fundamental reasons for resistances. Drawing on ethnographic research with a community of vaccine skeptics in southern California, a consideration of a leading vaccine researcher’s responses to vaccine critics and an analysis of Jenny McCarthy’s condemnation of current vaccine practices, this research considers why even parents who have accepted some vaccines, but not all, distrust vaccines and their proponents. Parents’ skepticism merits new forms of engagement by physicians and other vaccine advocates. As with any health intervention, vaccines can present some risks to a small number of recipients; when public health and clinical messages minimize parents’ fears, they may increase parental doubt. The voices of parents who choose to opt out of or to alter the normal vaccine schedule reveal important expressions of biomedical resistance.