Mumps has mutated and a NEW strain is now affecting vaccinated people.
Vaccination status was available for 278 cases of whom 84% had received at least one dose of mumps containing vaccine and 62% had received two.
This outbreak was genetically different from the previously circulating virus.
Source: Epidemiol Infect. 2017 Nov;145(15):3219-3225. doi: 10.1017/S0950268817002102. Epub 2017 Sep 14.