Efficacy of Air Cleaning Units for preventing SARS-CoV-2 and other hospital-acquired infections on medicine for older people wards: A quasi-experimental controlled before-and- after study.

Abstract

Nosocomial infections are costly and airborne transmission is increasingly recognised as important for spread. Air Cleaning Units (ACUs) may reduce transmission but little research has focused on their effectiveness on open wards. Assess whether ACUs reduce nosocomial SARS-CoV-2, or other, infections on older adult inpatient wards. Quasi-experimental before-after study on two intervention-control ward pairs in a UK teaching hospital. Infections were identified using routinely collected electronic health records data during one year of ACU implementation and the preceding year ("core study period"). Extended analyses included 6 months additional data from one ward pair following ACU removal. Hazard ratios (HR) were estimated through Cox regression controlling for age, sex, ward and background infection risk. Time the ACUs were switched on was also recorded for intervention ward 2. ACUs were initially feasible but compliance reduced towards the end of the study (average operation in first vs second half of ACU time on intervention ward 2: 77% vs 53%). 8171 admissions >48hrs (6112 patients, median age 85yrs) were included. Overall, incidence of ward-acquired SARS-CoV-2 was 3.8%. ACU implementation was associated with a non-significant trend of lower hazard for SARS-CoV-2 infection (HR core study period 0.90, 95% CI 0.53, 1.52; extended study period 0.78, 95% CI 0.53, 1.14). Only 1.5% of admissions resulted in other notable ward-acquired infections. ACUs may reduce SARS-CoV-2 infection to a clinically-meaningfully degree. Larger studies could reduce uncertainty, perhaps using a cross-over design, and factors influencing acceptability to staff and patients should be further explored.