Background: In response to recent outbreaks of vaccine-preventable diseases and concerns around vaccine refusal, several high-income countries have adopted or reformed vaccine mandate policies. While all make it more difficult for parents to refuse vaccines, the nature and scope of ‘mandatory vaccination’ is heterogeneous, and there has been no attempt to develop a detailed, comparative systematic account of the possible forms mandates can take. Methods: We compare the construction, introduction/amendment, and operation of six new high profile vaccine mandates in Australia, France, Germany, Italy, California, and Washington. We rank these policies in order of their relative restrictiveness and analyze other differences between them. Results: New mandate instruments differ in their effects on behavior, and with regard to their structure, exemptions, target populations, consequences and enforcement. We identify diverse means by which vaccine mandates can restrict behaviors, various degrees of severity, and different gradations of intensity in enforcement. Conclusion: We suggest that politico-cultural context and vaccine policy history are centrally important factors for vaccine mandate policymakers to consider. It matters whether citizens trust their governments to limit individual freedom in the name of public health, and whether citizens have previously been subjected to vaccine mandates. Furthermore, political communities must consider the diverse mechanisms by which they may construct vaccine mandate policies; whether through emergency decrees or ordinary statutes, and how (or whether) to involve various stakeholder groups in developing and implementing new vaccine mandate policies.