Mask use in the context of COVID-19 Interim guidance 1 December 2020 This document, which is an update of the guidance published patients wear the following types of mask/respirator in on 5 June 2020, includes new scientific evidence relevant to addition to other personal protective equipment that are the use of masks for reducing the spread of SARS-CoV-2, the part of standard, droplet and contact precautions: virus that causes COVID-19, and practical considerations. It ­ medical mask in the absence of aerosol contains updated evidence and guidance on the following: generating procedures (AGPs) • mask management; ­ respirator, N95 or FFP2 or FFP3 standards, or • SARS-CoV-2 transmission; equivalent in care settings for COVID-19 • masking in health facilities in areas with community, patients where AGPs are performed; these may cluster and sporadic transmission; be used by health workers when providing care • mask use by the public in areas with community and to COVID-19 patients in other settings if they cluster transmission; are widely available and if costs is not an issue. • alternatives to non-medical masks for the public; • In areas of known or suspected community or cluster • exhalation valves on respirators and non-medical masks; SARS-CoV-2 transmission WHO advises the following: • mask use during vigorous intensity physical activity; ­ universal masking for all persons (staff, patients, visitors, service providers and others) within the • essential parameters to be considered when health facility (including primary, secondary manufacturing non-medical masks (Annex). and tertiary care levels; outpatient care; and Key points long-term care facilities) ­ wearing of masks by inpatients when physical • The World Health Organization (WHO) advises the use distancing of at least 1 metre cannot be of masks as part of a comprehensive package of maintained or when patients are outside of their prevention and control measures to limit the spread of care areas. SARS-CoV-2, the virus that causes COVID-19. A mask • In areas of known or suspected sporadic SARS-CoV-2 alone, even when it is used correctly, is insufficient to transmission, health workers working in clinical areas provide adequate protection or source control. Other where patients are present should continuously wear a infection prevention and control (IPC) measures include medical mask. This is known as targeted continuous hand hygiene, physical distancing of at least 1 metre, medical masking for health workers in clinical areas; avoidance of touching one’s face, respiratory etiquette, • Exhalation valves on respirators are discouraged as they adequate ventilation in indoor settings, testing, contact bypass the filtration function for exhaled air by the tracing, quarantine and isolation. Together these wearer. measures are critical to prevent human-to-human transmission of SARS-CoV-2. Mask use in community settings • Depending on the type, masks can be used either for • Decision makers should apply a risk-based approach protection of healthy persons or to prevent onward when considering the use of masks for the general public. transmission (source control). • In areas of known or suspected community or cluster • WHO continues to advise that anyone suspected or SARS-CoV-2 transmission: confirmed of having COVID-19 or awaiting viral ­ WHO advises that the general public should laboratory test results should wear a medical mask when wear a non-medical mask in indoor (e.g. shops, in the presence of others (this does not apply to those shared workplaces, schools - see Table 2 for awaiting a test prior to travel). details) or outdoor settings where physical • For any mask type, appropriate use, storage and cleaning distancing of at least 1 metre cannot be or disposal are essential to ensure that they are as maintained. effective as possible and to avoid an increased ­ If indoors, unless ventilation has been be transmission risk. assessed to be adequate1, WHO advises that the general public should wear a non-medical mask, Mask use in health care settings regardless of whether physical distancing of at • WHO continues to recommend that health workers (1) least 1 metre can be maintained. providing care to suspected or confirmed COVID-19 1 For adequate ventilation refer to regional or national institutions recommended ventilation rate of 10 l/s/person should be met or heating, refrigerating and air-conditioning societies enacting (except healthcare facilities which have specific requirements). For ventilation requirements. If not available or applicable, a more information consult “Coronavirus (COVID-19) response Mask use in the context of COVID-19: Interim guidance ­ Individuals/people with higher risk of severe transparent and robust process of evaluation of the available complications from COVID-19 (individuals > evidence on benefits and harms. This evidence is evaluated 60 years old and those with underlying through expedited systematic reviews and expert consensus- conditions such as cardiovascular disease or building through weekly GDG consultations, facilitated by a diabetes mellitus, chronic lung disease, cancer, methodologist and, when necessary, followed up by surveys. cerebrovascular disease or immunosuppression) This process also considers, as much as possible, potential should wear medical masks when physical resource implications, values and preferences, feasibility, distancing of at least 1 metre cannot be equity, and ethics. Draft guidance documents are reviewed by maintained. an external review panel of experts prior to publication. • In any transmission scenarios: ­ Caregivers or those sharing living space with Purpose of the guidance people with suspected or confirmed COVID-19, regardless of symptoms, should wear a medical This document provides guidance for decision makers, public mask when in the same room. health and IPC professionals, health care managers and health workers in health care settings (including long-term care and Mask use in children (2) residential), for the public and for manufactures of non- • Children aged up to five years should not wear masks medical masks (Annex). It will be revised as new evidence for source control. emerges. • For children between six and 11 years of age, a risk- based approach should be applied to the decision to use WHO has also developed comprehensive guidance on IPC a mask; factors to be considered in the risk-based strategies for health care settings (3), long-term care facilities approach include intensity of SARS-CoV-2 (LTCF) (4), and home care (5). transmission, child’s capacity to comply with the appropriate use of masks and availability of appropriate Background adult supervision, local social and cultural environment, The use of masks is part of a comprehensive package of and specific settings such as households with elderly prevention and control measures that can limit the spread of relatives, or schools. certain respiratory viral diseases, including COVID-19. • Mask use in children and adolescents 12 years or older Masks can be used for protection of healthy persons (worn to should follow the same principles as for adults. protect oneself when in contact with an infected individual) • Special considerations are required for or for source control (worn by an infected individual to immunocompromised children or for paediatric patients prevent onward transmission) or both. with cystic fibrosis or certain other diseases (e.g., cancer), as well as for children of any age with developmental However, the use of a mask alone, even when correctly used disorders, disabilities or other specific health conditions (see below), is insufficient to provide an adequate level of that might interfere with mask wearing. protection for an uninfected individual or prevent onward transmission from an infected individual (source control). Manufacturing of non-medical (fabric) masks (Annex) Hand hygiene, physical distancing of at least 1 metre, • Homemade fabric masks of three-layer structure (based respiratory etiquette, adequate ventilation in indoor settings, on the fabric used) are advised, with each layer testing, contact tracing, quarantine, isolation and other providing a function: 1) an innermost layer of a infection prevention and control (IPC) measures are critical hydrophilic material 2) an outermost layer made of to prevent human-to-human transmission of SARS-CoV-2, hydrophobic material 3) a middle hydrophobic layer whether or not masks are used (6). which has been shown to enhance filtration or retain droplets. Mask management • Factory-made fabric masks should meet the minimum thresholds related to three essential parameters: For any type of mask, appropriate use, storage and cleaning, filtration, breathability and fit. or disposal are essential to ensure that they are as effective as • Exhalation valves are discouraged because they bypass possible and to avoid any increased risk of transmission. the filtration function of the fabric mask rendering it Adherence to correct mask management practices varies, unserviceable for source control. reinforcing the need for appropriate messaging (7). WHO provides the following guidance on the correct use of Methodology for developing the guidance masks: Guidance and recommendations included in this document • Perform hand hygiene before putting on the mask. are based on published WHO guidelines (in particular the • Inspect the mask for tears or holes, and do not use a WHO Guidelines on infection prevention and control of damaged mask. epidemic- and pandemic-prone acute