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Association between Airborne Infection Isolation Room Utilization Rates and Healthcare Worker COVID-19 Infections in Two Academic Hospitals

Our take —

This study directly examined the effect of utilizing airborne infection isolation room (AIIR) to treat COVID-19 patients on incidence of SARS-CoV-2 infections among healthcare staff at two major US hospitals in Boston with otherwise identical infection control protocols during March – August 2020. At one hospital 22% of COVID-19 patient days were spent in AIIRs, while at the other hospital, 96% of patient days were spent in AIIRs. Despite this, only 2% of patient-facing staff at each hospital was diagnosed with SARS-CoV-2 infection over the study time period. Also, the study found no differences in COVID-19 incidence rates between staff in patient-facing vs. non-patient-facing roles. While the study is unable to determine which infections were acquired from exposures at work versus in the community, this study suggests that using AIIRs resulted in no decrease in infection risk to staff, above and beyond the protection provided by other infection control practices.

Study design

Prospective Cohort

Study population and setting

The study objective was to measure the difference in healthcare worker SARS-CoV-2 infection rates in settings where there is high utilization of airborne infection isolation rooms (AIIR) compared to low utilization. The study was conducted at two hospitals in Boston, Massachusetts from March 1st to August 21st 2020: Massachusetts General Hospital, which has a limited number of AIIRs, and Brigham and Women’s hospital, which has multiple negative pressure wards for COVID-19. The two hospitals had identical infection control policies, given they are part of the same hospital center (Mass General Brigham), so the only differences were their use of AIIR. Universal masking was in place since March 22, and on April 10, both hospitals began recommending N95 respirators for all COVID-19 care, regardless of whether aerosol generating procedures were being conducted or not. The study calculated the ratio of hospitalization days for patients with confirmed COVID-19 in AIIRs versus standard pressure rooms for each hospital. The study then calculated weekly incidence rates among patient-facing vs. non-patient-facing roles, and fit an interrupted time series model to compare the incidence rates. Testing was available for any symptomatic staff, and beginning in early May, for any staff who experienced any unprotected exposures regardless of symptoms.

Summary of Main Findings

In total, 1,938 COVID-19 patients were admitted for 16,821 patient-days to MGH, and 1,142 patients were admitted for 8,529 patient-days to BWH. Patients at MGH spent 3,626 patient-days (22%) in AIIRs, and patients at BWH spent 8,157 (96%) patient-days in AIIRs. Of the 15,592 patient-facing employees at MGH, 2% (N=313) became infected with SARS-CoV-2, compared to 2% of 8,076 non-patient-facing employees (N=165). Of the 9,393 patient-facing BWH employees, 2% became infected (N=189), compared to 1.5% of non-patient-facing employees (108 cases among 7,251 employees). There were no statistically significant differences between the weekly infection rates at either hospital, and between patient-facing and non-patient-facing roles. Implementation of the N95 respirator policy on April 10 was not associated with any change in incidence of infection.

Study Strengths

They used two hospitals with identical infection control policies, which improved the ability of authors to make inferences about the contributions of airborne infection isolation rooms to infection control. In addition, the easy access that staff had to testing at these hospitals meant that is is unlikely that many infections among health care workers went unreported.


The study noted that many hospital staff were already using N95 respirators before the April 10 policy, which will reduce any differences in infection incidence before vs. after its implementation.

Value added

This study directly examines the impact of airborne infection isolation rooms on incidence of SARS-CoV-2 infections among healthcare workers at two hospitals who otherwise have identical infection control policies.

This review was posted on: 9 November 2021