I have had it once, aged 4 (am now 31) and my mum had it at the same time. Neither of us have ever had it since.
But then I have never been to hospital, never taken antibiotics, never had a chest, ear or any other form of infection. I haven't been to the Dr for anything other than family planning stuff since I was 12 (mumps).
Funnily enough though, when I was tested for immunity I wasn't immune to chicken pox or mumps, despite having had both.
So, just lucky I think (keeps fingers crossed at all times)