It's interesting that the CDC is saying 95% of the people that got the mumps were fully vaccinated, yet is responding to all this by ordering thousands more vaccination supplies and encouraging people to get vaccinated. Of course, vaccinations are big money for doctors...
Immune response typically wanes after vaccination, so revaccination can kickstart it again. It looks like the vaccine isn't terribly effective against this strain (it's from England), but reimmunizing is a rational move.
I wonder about those vaccinations. I got a flu shot back in November and I still got sick (3 times). I mean really sick. It happens everytime I decide to get a flu shot. My niece got a chicken pox vaccine. Guess what she's got now? Chickpox.