Interdependency in vaccination policies among Japanese municipalities.

Economic theory predicts that vaccination policies at the local level can be negatively affected by the policies of neighboring regions because of free-riding motives, whereas positive dependency may exist due to policy diffusions among localities. By using the unique variations in the provision of vaccination subsidies in Japan, we assess how vaccination policies in a local government are affected by the decisions of neighboring governments. We find that the provision of vaccination subsidies is positively correlated with the decisions of neighboring localities. Moreover, a correlation is found with neighboring municipalities within the same prefecture but not with those in surrounding prefectures, indicating that the correlations are likely to arise because of mimicking behavior among localities within a prefecture. Our results show that vaccination policies tend to be formed following neighboring municipalities and do not necessarily aim to optimize community health, thus questioning the autonomy of local government authorities regarding vaccination policies.