What is the probability of getting the mumps?

Depends: Most who have had the 2 dose vaccine in childhood have lifelong immunity. However, rates in the US have ranged between 300-6500 cases per year, mostly among older kids and young adults. Many cases of "mumps like illness" are other germs. Those living among people who do not vaccinate are at greater risk of exposure/disease if not immune.

Mumps : It depends on whether someone has had immunisation or not . Having two dosage is of vaccine gives 75-85 % protection.