The rate of influenza vaccination among healthcare workers (HCWs) is low, despite a good rationale and strong recommendations for vaccination from many health organizations.

To increase influenza vaccination rates by instituting the first mandatory influenza vaccination program for HCWs.

A 5-year study (from 2005 to 2010) at Virginia Mason Medical Center, a tertiary care, multispecialty medical center in Seattle, Washington, with approximately 5,000 employees.

All HCWs of the medical center were required to receive influenza vaccination. HCWs who were granted an accommodation for medical or religious reasons were required to wear a mask at work during influenza season. The main outcome measure was rate of influenza vaccination among HCWs.

In the first year of the program, there were a total of 4,703 HCWs, of whom 4,588 (97.6%) were vaccinated, and influenza vaccination rates of more than 98% were sustained over the subsequent 4 years of our study. Less than 0.7% of HCWs were granted an accommodation for medical or religious reasons and were required to wear a mask at work during influenza season, and less than 0.2% of HCWs refused vaccination and left Virginia Mason Medical Center.

A mandatory influenza vaccination program for HCWs is feasible, results in extremely high vaccination rates, and can be sustained over the course of several years.