[Brazil's national immunization program: origins and development].

The article discusses the central aspects of the trajectory of the National Immunization Program as regards the dynamics of sectoral policy. Heir to successful experiences of the past yet conceived at an entirely different moment, the Program followed the triumphant Campaign to Eradicate Smallpox and inaugurated a new phase in the history of public policy in the field of prevention. Under one sole command, the Program came to articulate a set of practices that had previously been spread across a number of government agencies and jurisdictions. The article examines the process by which the Program was conceived, structured, and developed within government health policy, and also underscores the main determinants of this policy, its institutional actors, and the political and ideological conflicts born of its implementation, whose success was an important component in the structuring of a vaccine market in Brazil.