[This article was originally published in Healthcare Policy 5(4).]

School-entry vaccination regulations are a policy instrument that has been widely used in some jurisdictions as a mechanism to ensure high immunization coverage rates. Exemptions to school-entry vaccination, which can be allowed on medical or non-medical grounds, present a number of ethical and policy challenges. In this paper, we consider the situation in Canada, where school-entry vaccination laws are rare. We present newly available aggregate-level registry data from Ontario comparing the use of medical and non-medical immunization exemptions to school-entry vaccination and the implications for population health.