[pella]

I prefer the antifragile metaphor.

"The immune system is an example of antifragility in the natural world since an effective response is only produced in the presence of an antigen threat, but the response leaves the body better able to respond in future. The presence of an antigen activates the immune response, which not only deals with the immediate challenge through the innate immune system in the short term and long term through the adaptive immune system but also provides ongoing protection against this and similar future threats through the immunological memory of B cells. In other words, exposure to an invading antigen leaves the body stronger than before, so the stressor has created a benefit that was neither present nor possible before it occurred."

read more: "Beyond resilience: towards antifragility?" https://scholar.google.com/scholar?cluster=13108278257209181...

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And see the -> https://en.wikipedia.org/wiki/Variolation

"Variolation was the method of inoculation first used to immunize individuals against smallpox (Variola) with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. Only 1–2% of those variolated died from the intentional infection compared to 30% who contracted smallpox naturally. Variolation is no longer used today. It was replaced by the smallpox vaccine, a safer alternative. This in turn led to the development of the many vaccines now available against other diseases."