The 2006 mumps outbreak where 6,600 people in the United States came down with the disease took health experts by surprise as nearly 80% of the people affected had received two mumps vaccinations in the past.

However, the vaccinations target a strain of mumps common in the U.S. The 2006 strain was a different version, believed to have been brought over from the United Kingdom where mumps vaccinations are not required and there was larger outbreak of the 2006 strain.

The current vaccination works well against the new strain, as proven in outbreaks elsewhere, but apparently can lose its effectiveness by the college years. As mumps is spread through respiratory secretions and saliva among people in close contact, it's not surprising that college students, who are generally packed into dorms, apartments, and lecture halls, made up the majority of patients in the 06 outbreak.

A third mumps shot before college is now being researched.