To extend the metaphor "develop immunity" a bit, I'd be curious about the mappings to: - vaccines, which build immunity by providing an inert or weak threat th

To extend the metaphor "develop immunity" a bit, I'd be curious about the mappings to: - vaccines, which build immunity by providing an inert or weak threat that the body builds resistance to. - herd immunity: restricts the spread of diseases if a sufficiently high proportion of the population is immune to the disease.