Recent studies indicate that the Rubini strain does not provide sufficient longterm clinical protection, although several other mumps vaccine strains do provide better long-term protection as demonstrated in outbreak investigations. Among the available strains, the rates of vaccine- associated aseptic meningitis vary; however, vaccine-associated meningitis resolves spontaneously in less than a week, and there are no sequelae. Natural
mumps infection leads to aseptic meningitis in up to 10% of patients, and this also resolves spontaneously within a week without sequelae. It is of far greater concern that natural mumps infection can lead to encephalitis, with a risk of death or permanent disability. Thus, countries need to consider that the incidence and severity of meningitis and encephalitis following natural infection greatly exceed those associated with any protective mumps vaccine currently available in international commerce (89).