Vaccination of health care workers (HCW) in long-term care results in indirect protection of patients who are at high-risk for influenza. The voluntary uptake of influenza vaccination among HCW is generally low. We argue that institutions caring for frail elderly have the responsibility to implement voluntary programmes for vaccination against influenza of HCW. When uptake falls short a mandatory programme may be justified. The main justification stems from the duty of care givers not to harm one's patient when one knows there is a significant risk of harm and the intervention to reduce this chance has a favourable balance of benefit over burdens and risks.