Henry Rider Haggard, the famed author of adventure romances, wrote the novelDr. Therne(1898) in response to weakening compulsory smallpox vaccination laws, thus entering one of the most heated debates of the late nineteenth century. WithDr. Therne,Haggard aimed to intervene in the lives of the many working-class anti-vaccinationists who, from the 1850s onwards, mobilised to evade what they perceived as a gross – and targeted – extension of state power at the expense of individual rights. Recovering the novel, which has not yet received scholarly attention from historians of medicine, reveals the way fiction was called upon to change minds during a crucial period of Victorian medicine, one that witnessed a climactic shift in public health intervention. This article will examine the reception ofDr. Thernein various print media – middle-class London papers, medical journals and working-class, anti-vaccinationist publications – to consider some new dynamics of the debate which the disagreement over Haggard’s polemic exposes, including the perceived power of fiction (when properly priced and distributed) to change minds, and the contested role of the evangelical press. Additionally, a discussion of the different iterations ofDr. Therne, and a look at an exceptional anti-vaccinationist response in the form of a competing novel, illustrates that pro- and anti-vaccinationists alike contributed to a moment in late Victorian society when the role of fiction was considered a worthy contender in a debate ostensibly about fact.