Impact of local vaccine subsidization programs on the prevention of mumps in Japan

In Japan, although a mumps vaccination is outside the national universal vaccination program, some local governments have implemented their own program. However, little is known regarding the implementation status and the impact of these programs. In this study, we investigated the impact on the prevention of mumps, after identification of the status of the local government subsidization programs. We identified the implementation status of the subsidization programs using the websites of local governments. We retrieved the number of reported mumps cases from designated sentinel sites through the Surveillance of Infectious Diseases System implemented according to the Infectious Disease Control Law. Using this data, the impact of the subsidization program on prevention of mumps was assessed by comparing the number of mumps cases per site during the 2015-2016 outbreak among the areas categorized by the subsidization status, using a Poisson regression model. As of 2019, 26.2% (456/1,739) of the local governments were considered as having subsidization programs. We retrieved 52,719 mumps cases from 2010 to 2019. The number of mumps cases per sentinel site tended to be low in areas implementing a subsidization program, compared with the no-implementation areas throughout the data collection period. The adjusted model confirmed that the subsidization program implemented between 2010 and 2015 impacted on the number of mumps cases during the 2015-2016 outbreak, with a decrease in the numbers. Further studies with detailed data including vaccination coverage should be conducted.