COVID-19 technical brief: Masking and face shields for full duration of shifts in acute healthcare settings

This document was created on April 15, 2020. Please refer back for future updates.

This technical brief represents an update to previously issued guidance and is applicable to acute healthcare settings. It applies to acute care settings such as hospitals; please see other guidance for primary care, community care settings, and long-term care.

Community transmission of COVID-19 infection continues to increase across Canada. It is recommended that all healthcare workers (HCWs) follow Routine Practices, including performing hand hygiene and a point-of-care risk assessment to determine the need for additional precautions and choice of personal protective equipment (PPE) during all patient encounters. Additional precautions for encounters with patients who have signs, symptoms, or known exposures to COVID-19, include wearing a mask, gown, gloves, and face or eye protection.

There is emerging evidence of unrecognized asymptomatic, pre-symptomatic, or pauci-symptomatic transmission of this virus. Both HCWs and patients admitted to hospital for other indications may be asymptomatic or have undetected pauci-symptomatic COVID-19 infection. Patients may also be incubating COVID-19 when admitted, but not become symptomatic until more than a week later.

In the context of increasing community transmission and the potential for asymptomatic, pre-symptomatic or pauci-symptomatic transmission, neither symptom-based or travel-based definitions are sufficiently reliable to identify infected patients and HCWs, increasing the risk of transmission to other patients and HCWs.

Physical distancing, environmental cleaning, and adherence to hand hygiene guidelines are essential. However, there is evidence of the introduction of COVID-19 into acute care facilities by both patients and HCWs despite efforts to improve these measures. There are also ongoing concerns about diminishing supplies of PPE in Canadian hospitals, and increasing focus on strategies to conserve existing PPE. This has led to consideration of additional measures to prevent transmission from HCWs to patients and other HCWs, and from patients to HCWs, including extended wearing of masks and eye protection for the full duration of HCW shifts.

The potential benefit of HCWs wearing a mask for the full duration of their shift is prevention of transmission of unrecognized COVID-19 infection to their patients or other HCWs (i.e., for use primarily as source control). Potential risks of wearing a mask continuously include risk of self-contamination through non-adherence to hand hygiene, inappropriate wear, or touching the mask, discomfort, skin irritation or breakdown, and a false sense of security that the wearer is fully protected by the mask.

The potential benefit of HCWs wearing eye protection (e.g., a face shield) in addition to a mask for the full duration of their shift is reduced exposure of HCWs to splash, spray, or droplets from patients who may be infected but not yet identified and placed under additional precautions (i.e., used as PPE). Potential disadvantages of wearing eye protection continuously also include the potential for self-contamination, altered clarity of vision, or discomfort.

There is variability in how these additional measures are being implemented across the country. Representatives of 78 acute care hospitals in the Canadian Nosocomial Infection Surveillance Program (CNISP) network were surveyed on April 8, 2020, asking if they are recommending masking of all HCWs with direct patient contact for the duration of their shifts. Forty-one (75%) of the 55 CNISP hospitals in 7/8 (88%) provinces represented in responses, are recommending masking of HCWs for the full duration of their shifts, and 7 (13%) others supported extended use not otherwise specified.

In the context of the COVID-19 pandemic, masking for the full duration of HCW shifts is recommended for those working in direct patient care areas, to reduce the risk of transmitting COVID-19 infection to patients or other HCWs. Use of eye protection (e.g., a face shield) for the full duration of HCW shifts should be strongly considered due to the increasing prevalence of COVID-19 infection. This guidance applies to all staff working within 2 metres of HCWs and patients. It is important to note that the masking strategy is intended to prevent transmission from asymptomatic or pre-symptomatic HCWs. HCWs with symptoms of illness that may be attributable to COVID-19 must be excluded from duty.

HCWs should refer to provincial and territorial guidance and facility policies on specific recommendations for use of masks, eye protection, and other PPE, and PPE conservation strategies. Provincial and territorial guidance will be informed by their specific epidemic curves. When masks and full-face shields are recommended for the full duration of shifts, HCWs must:

It is a foundational concept in infection prevention and control practice, that disposable masks should not be re-worn. However, in the context of the COVID-19 pandemic and PPE shortages, please refer to jurisdictional guidance with regard to mask use, re-use, and reprocessing policies.


This technical brief was prepared by: Cheryl Volling, Marina Salvadori, and James Brooks on behalf of the COVID-19 Clinical Issues Task Group

The authors gratefully acknowledge the contributions of: Allison McGeer, Gerald Evans, Kathryn Suh, Elizabeth Brodkin, Sandra Callery, Gordon Dow, Barb Catt on behalf of Infection Prevention and Control (IPAC)-Canada, and Linda Pelude and Robyn Mitchell, on behalf of the Canadian Nosocomial Infection Surveillance Program (CNISP).


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