The implementation of mandatory influenza vaccination policies among healthcare personnel (HCP) is controversial. Thus, we examined the affect of mandatory influenza vaccination policies among HCP working in outpatient settings.

Four Veterans’ Affairs (VA) health systems and three non-VA medical centers.

We analyzed rates of influenza and other viral causes of respiratory infections among HCP working in outpatient sites at 4 VA health systems without mandatory influenza vaccination policies and 3 non-VA health systems with mandatory influenza vaccination policies.

Influenza vaccination was associated with a decreased risk of influenza (odds ratio, 0.17; 95% confidence interval [CI], 0.13–0.22) but an increased risk of other respiratory viral infections (incidence rate ratio, 1.26; 95% CI, 1.02–1.57).

Our fitted regression models suggest that if influenza vaccination rates in clinics where vaccination was not mandated had equalled those where vaccine was mandated, HCP influenza infections would have been reduced by 52.1% (95% CI, 51.3%–53.0%). These observations, their possible causes, and additional strategies to reduce influenza and other viral respiratory illnesses among HCP working in ambulatory clinics warrant further investigation.