Mumps vaccine associated orchitis: Evidence supporting a potential immune-mediated mechanism.

We report 3 cases of orchitis following vaccination with mumps-measles-rubella (MMR) vaccine, two with an onset within 3 days following vaccination. Orchitis is a common complication of mumps infection, particularly in post-pubertal males, and is also recognized as a very rare complication of mumps vaccination. These cases, discussed together with a comprehensive review of the existing literature regarding post-vaccine orchitis, highlight uncertainty regarding the pathogenesis of post-vaccine orchitis.