Although influenza vaccination had been performed on mandatory basis for Japanese school-aged children until the mid of 1980s, thereafter the government changed the policy into individual-initiated basis. It caused the recipient rate of influenza vaccination rapidly decreasing. Consequently, there emerged a controversy about vaccination policy, mandatory vs. voluntary, for high-risk population. OBJECTIVE: Evaluate cost-consequences of the controversial strategies for influenza vaccination compared with no vaccination for healthy school-aged children in Japan. METHODS: A cost-consequence analysis was performed by decision analytic modeling using data from the literature. The decision tree models a healthy school-aged child facing the alternatives toward influenza: 1) individual-initiated voluntary vaccination; 2) mandatory vaccination in school; or 3) no vaccination. Direct costs included medical costs for vaccination (the costs of the vaccine, supplies, personnel, etc.), physician visits, and treatments. Also, indirect costs were included in the form of lost productivity in which the parents are burdened by taking children to a physician's office for vaccination or staying home to care for their ill children. The total cost of each scenario was compared with that of no vaccination consequence. We assumed the vaccine has no side effects for the base case, and then a sensitivity analysis was conducted to evaluate the impact of side effects with low-grade fever. RESULTS: Performing mandatory vaccination could save US$13 (JY1571) per child vaccinated comparing with no vaccination, whereas voluntary vaccination additionally cost US$36 (JY4428). Also, the total cost of mandatory scenario had an advantage of marginal saving of US$50 (JY6000) comparing to the voluntary basis. The sensitivity analysis indicated that results in the base case were rather robust. CONCLUSION: Mandatory vaccination for children in Japanese school could have substantial cost savings. Considering the target population of 18,000,000 school children in Japan, turning into mandatory is recommended with great potentiality of economic impact on the society.