The Arkansas Department of Health is investigating 2,918 confirmed cases of mumps and reports some of those cases involved children and adults who have been fully immunized. Mayo Clinic infectious diseases specialist Dr. Pritish Tosh says "The measles, mumps and rubella vaccine (MMR) is very good in preventing mumps but not perfect. And, so often we see a large group of people and maybe some of them are vaccinated, and mumps is introduced into that population, often by the people who are not vaccinated and they act as amplifiers of the infection. And, there are going to be some who were adequately vaccinated but because it's not 100 percent effective for mumps, close but not, you start to see cases not just in people who have not been vaccinated, but also in some people who have been adequately vaccinated."

Mumps is a contagious viral illness that typically starts with a few days of fever, headache, muscle aches, tiredness, and loss of appetite, followed by swollen salivary glands. "Most people who get mumps get swelling in the neck area, and it causes a fever, and for most people who get mumps, that’s the end of it. They get better on their own," says Dr. Tosh. "However, there are several complications. This used to be the No. 1 cause of sensorineural hearing loss in children and can cause infection in the brain."

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