In the following paper, we draw from Roberto Esposito's and Donna Haraway's theories of immunity to examine immigration apparatuses. The immunization perspective provides new ways of examining how immigration apparatuses function. In particular, we explore how they serve the purpose of biologically and culturally immunizing a nation from being contaminated by "dangerous" populations. We begin by briefly outlining Esposito's and Haraway's theories of immunity. Then for the remainder of the paper we provide a genealogical sketch of the demographics of immunization in Canadian immigration policies. In the Canadian case, there are two stages of immunization that roughly correspond to Esposito's historical account of the development of immunization apparatuses. First, we explore what we call the "crude immunization stage" (1867–1967), where various discriminatory criteria and measures were erected to safeguard the nation from being contaminated by populations designated as "dangerous." The second "sophisticated immunization stage" began when Canada adopted a more liberal notion of multiculturalism (1967–present). Despite making substantial changes to immigration policies in the late 1960s, which were supposed to drop all discriminatory criteria on the basis of race, ethnicity, or national origin, we demonstrate how the same categories were reasserted by streaming potential (im)migrants into two pools: valuable, high-skilled immigrant workers and disposable, low-skilled migrant laborers. In this second stage, Canada has increasingly relied upon "guest" workers over permanent immigrants to supply its labor market. This distinction between permanent immigrants and temporary migrants has become a new mechanism for discriminating on the basis of race, ethnicity, and national origin.