Changes in the mumps vaccine coverage and incidence of mumps before and after the public subsidization program: A descriptive study using a population-based database in Japan.

BACKGROUND

Continuous mumps vaccine coverage is essential for eradicating mumps. However, due to safety concerns, Japan's mumps vaccination program transitioned from routine to voluntary. To improve coverage, some municipalities introduced subsidization programs, but the effects on vaccination rates and mumps incidence remain unclear.

METHODS

In April 2018, a city in Japan launched a subsidization program for the mumps vaccine for children aged 1-6 years. Using vaccination records and healthcare claims from July 2016 to December 2019, we analyzed changes in vaccination coverage and mumps incidence before and after the program's initiation.

RESULTS

At the program's start, mumps vaccination coverage among eligible children was 3.3%, increasing by approximately 1.5% monthly to 38.4% after 21 months. Among 308,976 individuals, 145 mumps cases were identified: 92 cases (0.27 per 1,000 person-years) occurred before, and 53 (0.15 per 1,000 person-years) occurred after the program's start.

CONCLUSIONS

Although the mumps vaccination coverage rate increased following the program's initiation, it remained below the level required for eradication.