The number of mumps cases on the Harvard University campus has tripled since March.
There are now 40 students infected with mumps.
As of Monday, 11 students remained in isolation.
The health department says the infected students had all been vaccinated against mumps as, as required by law.
They say it’s possible the vaccine didn’t work in some people, or that the virus mutated in ways that made the shot less effective.
The director of Harvard University health services expressed concern that students may miss out on commencement ceremonies due to illness.
Mumps symptoms include puffy cheeks or jaws, as well as fever, headache and muscle-aches.
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