Recent arguments over whether certain public health interventions should be mandatory raise questions about what counts as a "mandate." A mandate is not the same as a mere recommendation or the standard of practice. At minimum, a mandate should require an active opt-out and there should be some penalty for refusing to abide by it. Over-loose use of the term "mandate" and the easing of opt-out provisions could eventually pose a risk to the gains that truly mandatory public health interventions, such as childhood vaccines, have provided over the last 50 years. Already, confusion about what counts as a mandate, and about what criteria should be used to determine when a public health intervention should be implemented as a mandate, has led to some inappropriate public policy decisions. For instance, by any reasonable criteria, the yearly influenza vaccine should be mandatory for health care workers. To enforce this mandate, those who refuse vaccination should be required to sign a waiver, and patients - especially those at high risk from flu - should be informed when they receive care from unvaccinated practitioners.