But if your child received all of his or her immunizations, there's no need to panic.
In fact, it's not really a surprise to see an outbreak of mumps or measles. We often get vaccinated when we're young, though nothing lasts forever.
Still, Dr. Steven Shapiro, chairman of pediatrics at Abington Hospital-Jefferson Health, reiterated that no vaccine offers complete protection, and the effectiveness does lessen over time.
"I say to every mom that I see, that vaccines are 95 percent (effective), but that still gives you a great deal of security," he said. "If everybody is protected at the 95th percentile, there's very little chance that the virus of particular concern at that time is going to enter that population."
If your child has been immunized and still gets the virus, Shapiro said he or she won't get as sick a kid who was never vaccinated.
The immunological term is drift, he explained, which represents that fact that vaccines wane after a number of years.
"We give a child its last dose of measles, mumps, rubella when they were 4 or 5 or 6 years old — before they enter kindergarten — and then they don't get it again, if ever, for the rest of their lives," he said.
At least one way to eliminate the fear of spreading the disease, Shapiro added, is to require everyone to get the vaccine.