Following this year's mumps outbreak, which resulted in 2,597 cases of the illness in the U.S., CDC has revamped the immunization recommendations in an attempt to better control mumps immunity. The Advisory Committee of Immunization Practices (ACIP) now defines acceptable presumptive evidence of immunity as: documentation of adequate vaccination, laboratory evidence of immunity, birth before 1957, or adequate vaccination-which is now defined as one dose of a live mumps vaccine for preschool-aged children and adults not at high risk, and two doses for school-aged children (grades K-12) and for adults at high risk (e.g., healthcare workers, international travelers, college students).