365Disease burden of mumps in Japan: descriptive epidemiology based on the health insurance reimbursement database

Abstract

Abstract Background In Japan, mumps vaccination coverage is low, since it is a voluntary vaccination. In this situation, the number of mumps cases as reported by pediatric sentinel hospitals suggests the occurrence of periodical mumps outbreaks. Methods To examine the annual incidences of mumps and mumps-related complications, we analyzed data from the health insurance reimbursement database for subscribers aged 0-64 years between 2005 and 2017. Cases with mumps and mumps-related complications including meningitis, orchitis, deafness, were extracted according to ICD-10 codes entered into the disease section for health insurance reimbursement. Results During the 13 year period, 68,307 of 5,209,660 subjects were reimbursed for mumps, with an incidence of 325 per 100,000 person-years (95% confidence interval (CI): 323-328). Among the 68,307 mumps cases, 787 were reimbursed for mumps-related complications, with an incidence of 11.5 per 1,000 mumps cases (95% CI: 10.7-12.4). Incidence of mumps-related complications (per 1,000 mumps cases) was highest for orchitis (6.6), followed by meningitis (5.8), deafness (1.3), pancreatitis (0.5), and encephalitis (0.3). Mumps incidence was highest among children aged 0-5 years, while incidence of mumps-related complications was highest among adults aged 26-35 years. Conclusions In Japan, the disease burden of mumps remains high among adults, as well as children. Key messages To reduce the disease burden of mumps among all ages in Japan, immunization in childhood is required. A national immunization program for children would result in high vaccination coverage and lower disease burden.