The resurgence of vaccine-preventable diseases is a fascinating, if unwanted, phenomenon. Pertussis, measles, and now mumps are cropping up after long periods of quiescence. Mumps has been generally very well-controlled since the adoption of wide-spread vaccination, with no nation-wide outbreaks, but there have been a number of regional outbreaks, most notably in 2006 and now again in 2009. Since the widespread use of two-dose vaccines, mumps cases in the US have dropped by more than 99%.
In an analysis of the 2006 outbreak the authors noted a three year periodicity to wide-spread mumps epidemics,and predicted a 2009 outbreak similar to the 2006 outbreak based on pre-outbreak epidemiology.. It appears they were right. The CDC is reporting a sudden outbreak among a religious community in the Northeast (they don't say it explicitly but it appears to be an Orthodox Jewish community). The disease appears to have been imported from an ongoing UK outbreak, and then to have spread through the close quarters of a summer camp. As children returned home from camp, the disease spread through their communities.
Barskey, A., Glasser, J., & LeBaron, C. (2009). Mumps resurgences in the United States: A historical perspective on unexpected elements☆ Vaccine, 27 (44), 6186-6195 DOI: 10.1016/j.vaccine.2009.06.109
"Mumps Outbreak --- New York, New Jersey, Quebec, 2009." MMWR: Morbidity and Mortality Weekly Report November 12, 2009 / 58(Dispatch);1-4.