The term immunity came into the 21st century with many meanings relevant to the superthreats, from Quarantine (physical immunity) to Outlaw Planet (criminal immunity) to Generation Exile (immigration immunity). But the concept of immunity has now taken on a broader meaning, reflecting the capacity of an individual, an organization, or an entire community to resist harm from external threats.
As such, it applies to much more than disease. People talk of immunity to cultural changes, political threats, even technologies. Their "immune systems" include large ecologies of relationships, skills, and resources. The extended metaphor surfaces in discussions of social auto-immune disorders, community "t-cells" (the actors or forces promoting immunity), immunological memory, even immunodeficiency.
Immunity, immune systems, and immunization are all terms that people use to talk about human problems and their solutions.