Vaccination rates among health care workers are less than 50%, well below the level necessary for herd immunity. Employers planning to implement mandatory influenza vaccination policies for health-care workers need to understand the implications, according to experts. In Canada, condition-of-service policies must comply with employment law, provincial human rights codes and the Canadian Charter of Rights and Freedoms. Condition-of-service policies that apply to unionized employees must be consistent with collective labour agreements, and vaccination policies should allow exemptions for religious beliefs and practices.