Here’s a graphic from Alberta Health on vaccination rates in southern Alberta for measles by town and region.
Note that anything <80% creates conditions for a sustained epidemic. The AHS goal is 98% coverage, which is about what is needed for herd immunity to keep any cases from developing.
Note too that metro Lethbridge (due north of Spring Coulee, in the approx centre of the map) is in the 80-90% range, and yet that is where the outbreak began and is persisting for the moment. So 80-90% doesn’t cut it.
And, a second slide gives some of the complications that attend the illness.
They don’t mention SSPE, which can afflict the brains of measles patients even decades later.