Mumps is a disease of childhood in places where it's endemic and prevalent, which would suggest most immigrant communities would not actually be the source, tho

Mumps is a disease of childhood in places where it's endemic and prevalent, which would suggest most immigrant communities would not actually be the source, though for very small clusters, small ethnic or religious communities (not necessarily foreign ones - the Dutch outbreaks for example are just religious groups) can be the source. As for some of the other countries in Europe, while there's less of a vocal anti-vaxx movement, the vaccination rate in the Swiss has been dropping for the better part of a decade now.