The number of mumps cases at the University of Iowa (UI) has topped the 150 mark as health officials report 152 cases, 78 percent of the 196 lab-confirmed cases in Johnson County and 63 percent of the 241 cases reported statewide since July 12, according to local media.

A third dose of the measles-mumps-rubella (MMR) vaccine has been available for free for students age 24 and under and will continue through the end of the day on Wednesday, December 23, 2015.

Some 5,000 UI students were vaccinated in November at a cost of more than $250,000, The Gazette reports.

As of Dec. 11, 853 mumps cases have been reported to the Centers for Disease Control and Prevention (CDC) nationally.

Mumps is an infection caused by the mumps virus. Mumps is spread by droplets of saliva or mucus from the mouth, nose, or throat of an infected person, usually when the person coughs, sneezes or talks. Items used by an infected person, such as cups or soft drink cans, can also be contaminated with the virus, which may spread to others if those items are shared.