Though it is a centuries old practice, anti-vaccination has become a growing trend since the rise of the internet. Anti-vaccination rhetoric complicates neoliberal beliefs about public health and systems of medical knowledge-making. This study follows 100 Twitter accounts which advance anti-vaccination beliefs. Studying these accounts reveals that anti-vaccination is part of a larger moral and epistemological universe of belief. Anti-vaccination advocates on Twitter use a digital activist identity to create affective networks which draw from epistemologies of conspiracy theory and connect to current political events. Anti-vaccination advocates on Twitter are not uninformed. Rather, they ascribe to their own process of information legitimization. Anti-vaccination advocates on Twitter draw from their complex epistemologies and affective networks to build an alternative immunology which focuses on maintaining the purity of the individual body as a metaphor for protection of the state and of humanity