Doctors Agree: Ineffective Vaccine Responsible for Hockey League Mumps EpidemicPast generations of professional hockey players were never at risk of mumps outbreaks. Today's players are, and tomorrow's will be, along with adults generally. These outbreaks -- which the media portray as coming out of the blue -- don't surprise anyone in medical circles who has been paying attention. Mumps outbreaks among adults have long been predicted by public health experts. Ironically, the mumps vaccine itself makes these outbreaks inevitable.