[lotsofpulp]

No, it’s free in the US too. There are clusters of families in communities that reject vaccines however, so there are a bunch of schools with insufficient proportions of vaccinated kids. A ripe breeding ground to create a vaccine resistant strain of measles or mumps or whatever.

[Vecr]

Vaccine resistant measles does not appear to be possible using standard gain-of-function methods on the vaccine strain, mumps I have no clue. People's vaccines wearing off (or not working in the first place) and them not noticing due to herd immunity would be a much bigger problem, I think.