What are the chances of catching mumps when immunised?

[maddiemo]

Ds3 who is nine has had his his mmr and booster. However I suspect he may have mumps. There is currently and outbreak at ds1's senior school.

Is this likely? He has temp of 39, swollen face especially cheek and jaw on one side and feels generally under the weather.

Two of my DSs have had measles after having the first MMR, so would imagine it is possible to get mumps even after the booster.

There's been a bit of an outbreak at local secondary schools here too. Those children are old enough to have had MMR but I'm not sure if they would have had boosters. My 13 year old did but my 16 year old didn't (think his was this first year they had MMR).