Background Evidence that hand hygiene (HH) reduces healthcare-associated infections has been available for almost two centuries. Yet HH compliance among healthcare professionals continues to be low, and most efforts to improve it have failed.

Objective To improve healthcare workers' HH, and reduce healthcare-associated infections.

Design 3-year interrupted time series with multiple sequential interventions and 1-year post-intervention follow-up.

Setting Teaching hospital in rural New Hampshire.

Interventions In five categories: (1) leadership/accountability; (2) measurement/feedback; (3) hand sanitiser availability; (4) education/training; and (5) marketing/communication.

Measurement Monthly changes in observed HH compliance (%) and rates of healthcare-associated infection (including Staphylococcus aureus infections, Clostridium difficile infections and bloodstream infections) per 1000 inpatient days. The subset of S aureus infections attributable to the operating room served as a tracer condition. We used statistical process control charts to identify significant changes.

Results HH compliance increased significantly from 41% to 87% (p<0.01) during the initiative, and improved further to 91% (p<0.01) the following year. Nurses achieved higher HH compliance (93%) than physicians (78%). There was a significant, sustained decline in the healthcare-associated infection rate from 4.8 to 3.3 (p<0.01) per 1000 inpatient days. The rate of S aureus infections attributable to the operating room rose, while the rate of other S aureus infections fell.

Conclusions Our initiative was associated with a large and significant hospital-wide improvement in HH which was sustained through the following year and a significant, sustained reduction in the incidence of healthcare-associated infection. The observed increased incidence of the tracer condition supports the assertion that HH improvement contributed to infection reduction. Persistent variation in HH performance among different groups requires further study.