It doesn't apply to non-humans because herd immunity is not something that is at all related to non-human populations. The term was coined to describe a trait o

It doesn't apply to non-humans because herd immunity is not something that is at all related to non-human populations. The term was coined to describe a trait of human populations and was found to be difficult if not impossible to achieve in humans until we started to vaccinate. https://en.wikipedia.org/wiki/Herd_immunity#History https://en.wikipedia.org/wiki/Herd_immunity#History