Use of N95, Surgical, and Cloth Masks to Prevent COVID-19 in Health Care and Community Settings: Living Practice Points From the American College of Physicians (Version 1).

Key Question 1

What is the effectiveness of N95 respirators versus surgical masks versus cloth masks for the prevention of coronavirus disease 2019 (COVID-19) in addition to standard precautions (gloves + handwashing) in community settings?

Key Question 2

What is the effectiveness of N95 respirators versus surgical masks versus cloth masks for the prevention of COVID-19 in addition to standard precautions (gowns + gloves + handwashing) in health care settings?

Key Question 3

What is the effectiveness for reuse or extended use of N95 respirators for prevention of COVID-19?

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads among persons in close proximity through droplets, although evidence is still emerging regarding potential airborne transmission. Reducing transmission of SARS-CoV-2 infection in health care and community settings is a major priority, especially in the absence of an effective vaccine or treatment. The use of respiratory personal protective equipment (PPE) may decrease the risk for respiratory infection, although controversy exists around the appropriate types of masks and the situations in which they should be used in community and health care settings for the prevention of SARS-CoV-2 infection. The following practice points (Table 1) are intended for clinicians, patients, and the public. Data on SARS-CoV-2 are limited. These practice points are based on the best available evidence on the effectiveness of N95 respirators, surgical masks, and cloth masks in reducing transmission of infection with SARS-CoV-1, Middle East respiratory syndrome coronavirus (MERS-CoV), and influenza-like or other respiratory viruses in community and health care settings. Evidence about reuse or extended use of N95 respirators in health care settings was also considered.

Table 1. Practice Points

The American College of Physicians (ACP) based these practice points on a rapid, living systematic evidence review funded by the Agency for Healthcare Research and Quality (1, 2). See the Appendix for methods used to develop the practice points. This version of the practice points, based on an evidence review completed on 14 April 2020 with surveillance through 2 June 2020, was approved by the ACP's Executive Committee of Board of Regents on behalf of the Board of Regents on 18 May 2020, and submitted to Annals of Internal Medicine on 13 May 2020. Ongoing surveillance of the literature is planned for 1 year from the initial search date, and the living practice points will be updated alongside the evidence review.

Evidence description.

Evidence search and assessment conducted by the Pacific Northwest Evidence-based Practice Center and funded by the Agency for Healthcare Research and Quality (2). Current search for evidence, completed on 14 April 2020 and updated through 2 June 2020, aimed to identify RCTs and OBSs on the use of N95 respirators, surgical masks, and cloth masks to prevent SARS-CoV-2 infection and coronaviruses (SARS-CoV-1, MERS-CoV) infections and RCTs of N95 respirators, surgical masks, and cloth masks to prevent influenza-like (influenza or other respiratory viruses) infections, as well as all studies on the reuse/extended use of N95 respirators. MERS-CoV = Middle East respiratory syndrome coronavirus; OBS = observational study; PCP = primary care physician; PPE = personal protective equipment; RCT = randomized controlled trial; SARS-CoV-2 = severe acute respiratory syndrome 2.

* Different types of respiratory PPE intervention were generally used in addition to additional PPE required for droplet precautions (e.g., gowns, gloves) and hand hygiene in health care settings.

Rationale

What is the effectiveness of N95 respirators, surgical masks, and cloth masks for the prevention of COVID-19 in addition to standard precautions (gloves + handwashing) in community settings?

The goal of using N95 respirators, surgical masks, or cloth masks is to prevent transmission of SARS-CoV-2 infection from asymptomatic or symptomatic infected persons to uninfected persons (source control). Currently, no direct evidence exists for the effectiveness or comparative effectiveness of various types of respirators or masks for preventing SARS-CoV-2 infection in community settings. Low-certainty evidence showed that mask use may reduce the risk for SARS-CoV-1 infection compared with no mask use in the community, but a major limitation of the studies is that they did not specify mask type. Low-certainty indirect evidence also found that N95 respirators may not reduce the risk for noncoronavirus respiratory infections compared with surgical masks or no masks, and moderate-certainty indirect evidence showed that surgical masks probably do not reduce the risk compared with no masks. For surgical masks, there was moderate-certainty evidence of nonserious harms, such as discomfort and difficulty in breathing, compared with no mask use, and low-certainty evidence showed that N95 respirators may not increase discomfort compared with surgical masks. The review identified no eligible studies on the use of cloth masks in community settings.

N95 respirators should not be used in a community setting, given the absence of demonstrated benefit, the possible harm with improper use (that is, the requirement for fit testing), and the global shortage of N95 respirators. Unlike N95 respirators, surgical masks and cloth masks do not require special fitting, making their use more practical if individual fitting is infeasible. Persons should seek guidance from the local community and statewide public health guidelines for mask use in light of the absence of evidence in the community setting to reduce the risk for transmission of SARS-CoV-2 infection. Factors to consider include exposure context (number of people, whether indoors or outdoors, ventilation), epidemiologic data (such as reproduction rate, daily case counts, hospitalizations, and deaths), and local demographics (such as high-risk populations). Individual values and preferences should be taken into account when deciding on the type of mask to use (surgical or cloth mask), because the benefits and harms for surgical versus cloth masks are finely balanced. The use of cloth masks in community settings has been encouraged by the Centers for Disease Control and Prevention (CDC) (4). The World Health Organization (WHO) recommends a risk-based approach for decision makers when recommending use of nonmedical masks, such as cloth masks, in the community setting (6). The WHO notes potential risks associated with mask use, including self-contamination (via improper handling of masks), breathing difficulties, and a false sense of security that could potentially detract from taking other precautions, such as physical distancing (6). Regardless of mask type, clinicians and public health officials should educate the general public about appropriate mask use (Table 3).

Table 3. Appropriate Use and Disposal of N95 Respirators, Surgical Masks, and Cloth Masks

Persons at highest risk for SARS-CoV-2 infection are those who are in close contact with persons who have COVID-19 (7, 8). When in close contact with others, persons experiencing symptoms and those in contact with them should wear a surgical mask or cloth mask. A person who interacts with many people (such as flight attendants, restaurant servers, grocery store workers, cab drivers, and others) may benefit from wearing a surgical or cloth mask. The use of masks is not necessary when at home, unless a household member has COVID-19.

What is the effectiveness of N95 respirators, surgical masks, and cloth masks for the prevention of COVID-19 in addition to standard precautions (gowns + gloves + handwashing) in health care settings?

The goal of using respiratory PPE is to reduce exposure and prevent SARS-CoV-2 transmission between health care personnel and patients. Currently, direct evidence on the effectiveness or comparative effectiveness of N95 respirators and surgical masks for preventing SARS-CoV-2 infection in health care settings is insufficient. Given the limited direct evidence, our practice points are based on indirect evidence from studies of SARS-CoV-1, MERS-CoV, influenza or influenza-like infections, and other respiratory infections.

Low-certainty evidence showed that mask use and consistent mask use may reduce the risk for SARS-CoV-1 infection compared with no mask use and inconsistent mask use in health care settings, but studies did not specify mask type. Low-certainty indirect evidence showed that N95 respirators may reduce the risk for SARS-CoV-1 infection compared with surgical masks or no masks. Indirect evidence from studies reporting on the risk for noncoronavirus respiratory infections showed that N95 respirators probably do not reduce the risk for noncoronavirus respiratory infections compared with surgical masks (moderate certainty) and that surgical masks may reduce the risk for clinical respiratory illness, laboratory-confirmed viral infections, and influenza-like illness compared with cloth masks (low certainty). Indirect evidence was insufficient about the effect of N95 respirators or surgical masks compared with cloth masks, and surgical masks and cloth masks compared with no masks, on the risk for SARS-CoV-1 infection. Low-certainty evidence showed that N95 respirators may increase some nonserious harms, such as discomfort, breathing difficulties, and headache, compared with surgical masks and moderate-certainty indirect evidence that those harms probably do not increase with the use of surgical masks compared with cloth masks.

Uncertainty about airborne transmission of SARS-CoV-2 continues (9). Health care workers are at an increased risk for infection, because they are more likely to be in close contact with patients who are confirmed or suspected to have COVID-19. The CDC does not consider cloth masks as PPE in health care settings, given the lack of evidence of their effectiveness against transmission of SARS-CoV-2 (10).

Health care personnel should not be exposed to patients suspected or known to have COVID-19 without proper PPE. It is essential to strictly follow all other infection prevention and control measures (such as hand hygiene, physical distancing, and others) along with appropriate use of other PPE (such as gowns, gloves, and goggles) in health care settings.

What is the effectiveness for reuse or extended use of N95 respirators for prevention of COVID-19?

Extended use is defined as wearing the same N95 respirator without removal between patient encounters (5). Reuse is defined as using the same N95 respirator for several encounters with patients but removing it after each encounter (5). Currently, no evidence is available about the effectiveness of extended use or reuse of N95 respirators in health care settings. However, on the basis of an assessment of nonclinical outcomes (such as measures of filtration, contamination, and mask failure), a previous review comparing extended use and reuse of N95 respirators concluded that extended use of N95 respirators is preferable to reuse of N95 respirators because it involves less touching of the respirator, thus less risk for contact transmission (11).

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Table 2. Clinical Considerations

Table 4. Evidence Summary: What Information Does the Evidence Provide?