Is aseptic meningitis following mumps vaccination underreported in Japan?

The definitive diagnosis of aseptic meningitis is made by analyzing the cerebrospinal fluid, which requires lumbar puncture (an invasive procedure) that is usually not performed if the patient has mild symptoms. [...]symptomatic management is the mainstay of therapy in aseptic meningitis. [...]it can be concluded that the incidence of mumps vaccine-related meningitis in Japan may be much higher than the frequency currently reported. The funding source had no role in study design, or in the collection, analysis, and interpretation of data, in the writing of the report, or in the decision to submit the article for publication.