Penn State has seen about 30 cases of mumps at the University Park campus since January. Of those, all of the people affected had been vaccinated.
Shelley Haffner, infectious disease manager at Penn State, said no vaccine is 100 percent effective for 100 percent of the population.
“There are a lot of unknowns still with this," Haffner said. "We’re working with the Pennsylvania Department of Health who is also working with the CDC (Centers for Disease Control) to look at this because we’re seeing more mumps outbreaks on college campuses in recent years.”