Because of the concerns about aseptic meningitis due to Japanese domestic mumps vaccine strains, the routine mumps immunization program has not yet been introduced in Japan, and it resulted in the situation where the major mumps epidemics occur every 4-5 years. However, the fact that at least 348 mumps hearing loss cases were reported during the recent epidemic period in 2015-2016, argues that the introduction of the routine mumps immunization program is an urgent issue for us. In contrast, 122 countries employ mumps-containing vaccines for nationwide immunization programs by 2018, of which 117 apply 2-dose vaccination regimens, and many of them use Jeryl-Lynn containing measles-mumps-rubella (MMR) vaccines. While in these countries, where mumps seemed to have been controlled, mumps resurgented in the 2000s. Although, the concerns surrounding mumps vaccination are extremely different in Japan and abroad, both of them link to the inherent characteristics of mumps vaccine, in which it is hard to balance the safety and the efficacy. In order to promptly introduce the routine mumps immunization program in Japan, Japanese domestic mumps vaccine strains need to be re-evaluated based on the latest evidence. Furthermore, from a long-range viewpoint, a novel mumps vaccine should be developed, which combines the safety and the efficacy.