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VIRGINIA (CBSMiami) — Health officials at a Virginia university are dealing with a mumps outbreak. In recent years, more and more young adults who are vaccinated are coming down with the illness.

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Now a new study indicates why there has been a resurgence in cases.

At James Madison University in Virginia, 24 cases of the mumps have been reported among students and staff since January.

The U.S. has seen more outbreaks of mumps in vaccinated young adults, which spreads through close contact.

New research from Harvard T.H. Chan School of Public Health shows the increase is likely because protection can decline years after receiving the vaccine.

“We expect 50 percent of people to retain protection for 19 years after receiving a mumps-containing vaccine. Many people will maintain protection far longer, so the population average is about 27 years,” said study author. Joseph Lewnard, Research Associate, Harvard T.H. Chan School of Public Health.

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Mumps is known for causing puffy cheeks and a swollen jaw because the salivary glands become enlarged. Other common symptoms include fever, headache and muscle aches.

Currently, children receive the Measles Mumps Rubella vaccine at 1-year-old and then between 4 and 6.

While the vaccine is nearly 90 percent effective after two doses, Lewnard says their findings suggest a third booster dose may help cut down on future cases.

“Additional doses, either in response to outbreaks or to prevent outbreaks, might be warranted,” said Lewnard.

Last year, there were over 5,600 cases of mumps reported in the U.S. with infections on several college campuses as well as with NHL players.

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Most people with mumps have a complete recovery in a few weeks but severe infections may cause complications that can cause meningitis, deafness and affect fertility in men.