Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings: A Living Rapid ReviewFREE
Submit a Comment
Contributors must reveal any conflict of interest. Comments are moderated. Please see our information for authorsregarding comments on an Annals publication.
Abstract
An update is available for this article.
Background:
Recommendations on masks for preventing coronavirus disease 2019 (COVID-19) vary.
Purpose:
To examine the effectiveness of N95, surgical, and cloth masks in community and health care settings for preventing respiratory virus infections, and effects of reuse or extended use of N95 masks.
Data Sources:
Multiple electronic databases, including the World Health Organization COVID-19 database and medRxiv preprint server (2003 through 14 April 2020; surveillance through 2 June 2020), and reference lists.
Study Selection:
Randomized trials of masks and risk for respiratory virus infection, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and observational studies of mask use and coronavirus infection risk were included. New evidence will be incorporated by using living review methods.
Data Extraction:
One reviewer abstracted data and assessed methodological limitations; a second reviewer provided verification.
Data Synthesis:
39 studies (18 randomized controlled trials and 21 observational studies; 33 867 participants) were included. No study evaluated reuse or extended use of N95 masks. Evidence on SARS-CoV-2 was limited to 2 observational studies with serious limitations. Community mask use was possibly associated with decreased risk for SARS-CoV-1 infection in observational studies. In high- or moderate-risk health care settings, observational studies found that risk for infection with SARS-CoV-1 and Middle East respiratory syndrome coronavirus probably decreased with mask use versus nonuse and possibly decreased with N95 versus surgical mask use. Randomized trials in community settings found possibly no difference between N95 versus surgical masks and probably no difference between surgical versus no mask in risk for influenza or influenza-like illness, but compliance was low. In health care settings, N95 and surgical masks were probably associated with similar risks for influenza-like illness and laboratory-confirmed viral infection; clinical respiratory illness had inconsistency. Bothersome symptoms were common.
Limitations:
There were few SARS-CoV-2 studies, observational studies have methodological limitations, and the review was done by using streamlined methods.
Conclusion:
Evidence on mask effectiveness for respiratory infection prevention is stronger in health care than community settings. N95 respirators might reduce SARS-CoV-1 risk versus surgical masks in health care settings, but applicability to SARS-CoV-2 is uncertain.
Primary Funding Source:
Agency for Healthcare Research and Quality.
Clinicians and policymakers recommend preventive measures, including use of respiratory protective devices, to reduce the risk for coronavirus disease 2019 (COVID-19), the disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is thought that SARS-CoV-2 is spread primarily through contact and large respiratory droplets, but evidence also indicates potential transmission by fine respiratory aerosols (1). Several types of respiratory protective devices (collectively referred to as “face masks”) are available (2). Disposable N95 and equivalent respirators are fitted devices that have been tested to achieve very efficient filtration of small airborne particles, including aerosols. Surgical or medical masks (hereafter referred to as “surgical masks”) are loose-fitting, create a physical barrier, block larger particles, and are fluid-resistant. Cloth masks are nonmedical face coverings that vary with regard to filtration and fluid resistance depending on the material used, the number of layers, and fit. Single-use N95 and equivalent respirators provide higher respiratory protection than surgical masks (3), but shortages have been reported (4). Extended use and reuse of N95 respirators have been tested in laboratory settings (5), but clinical effectiveness and safety are uncertain (5, 6).
This living rapid review addresses the comparative effectiveness of face masks in community and health care settings for prevention of SARS-CoV-2 infection and associated COVID-19 disease, and the effectiveness and safety of mask reuse. This report will be used by the American College of Physicians (ACP) to develop evidence-based practice points on mask use in different settings. Because evidence is limited on SARS-CoV-2, this review also includes evidence on SARS-CoV-1 (causing SARS-1) and Middle East respiratory syndrome coronavirus (MERS-CoV) (causing MERS) and other viral respiratory illness (including influenza and influenza-like illness).
Methods
Detailed methods are available in the full report (7). The key questions were developed with input from staff at ACP and the Agency for Healthcare Research and Quality (AHRQ), with input from the review authors.
Key Question 1a. What is the effectiveness and comparative effectiveness of respirators (N95 or equivalent), face masks (surgical), and cloth masks in addition to standard precautions in community and health care (high- or non–high-risk) settings for prevention of SARS-CoV-2 infection?
Key Question 1b. For SARS-CoV-1 or MERS-CoV infection?
Key Question 1c. For influenza, influenza-like illness, and other viral respiratory infection?
Key Question 2. What is the evidence for extended or reuse of N95 respirators for prevention of SARS-CoV-2, SARS-CoV-1, or MERS-CoV infection?
Owing to the urgent and ongoing nature of the COVID-19 pandemic, a rapid, living review approach was used (8). Rapid reviews utilize streamlined systematic review processes. For this review, modified methods included 1) a gray literature search limited to 1 website; 2) dual review of excluded abstracts only; 3) critical appraisal of observational studies not conducted by using a formal instrument; and 4) critical appraisal and data abstraction by a single reviewer, with verification by a second reviewer. Living reviews use methods for continually updating, as new evidence becomes available (9).
Data Sources and Searches
A medical librarian searched PubMed, MEDLINE, and Elsevier Embase (from 2003 through 14 April 2020). Search strategies are shown in Supplement Table 1. We also searched the World Health Organization (WHO) COVID-19 database (10) and the medRxiv preprint server (11) and reviewed reference lists of relevant articles, including a living review on risk factors (including mask use) for coronavirus infections in health care workers (HCWs) (12). Daily MEDLINE surveillance and weekly surveillance on EMBASE, the WHO database, and the medRxiv server is ongoing; this article includes surveillance through 2 June 2020.
Study Selection
Studies were selected by using predefined criteria (Supplement Table 2). The population was HCWs and persons in the community. Interventions were disposable N95 filtering facepiece respirators, surgical masks, and cloth masks. For key question 1, we included randomized controlled trials (RCTs) of one mask type versus another that reported effects on risk for infection with SARS-CoV-2 (including infections meeting criteria for COVID-19), SARS-CoV-1 (including SARS-1), or MERS-CoV (including MERS); influenza-like illness; laboratory-confirmed viral respiratory illness; and harms. To inform indirect comparisons, we also included RCTs of masks versus no masks. We included cohort and case–control studies on the association between mask use and risk for COVID-19, SARS-1, and MERS, owing to the lack of randomized trials for these outcomes. Studies on noncoronavirus infections were restricted to randomized trials, because such studies are available. We also included studies on reuse or extended use of masks versus standard use and risk for SARS-CoV-2, SARS-CoV-1, or MERS-CoV infection.
One investigator reviewed each citation for potential full-text review and reviewed each full-text article for inclusion. A second investigator verified exclusion decisions at both the citation and full-text level; disagreements were resolved through consensus. We included non–peer-reviewed articles for SARS-CoV-2 because peer-reviewed literature was sparse. Chinese-language articles were translated by a native speaker.
Data Extraction
One investigator extracted study data into standardized tables, and a second verified data: study author, year, setting (country, health care setting, dates), population characteristics (sample size, age, sex, HCW role or position, number of cases, exposures, personal protective equipment use), mask interventions (randomized trials, including adherence) or mask use (observational studies), and results. If necessary, we calculated relative risks (randomized trials) and odds ratios (observational studies) from available data. For observational studies on HCWs and coronavirus, we categorized risk settings as high (coronavirus infection exposures in intensive care units, frequent aerosol-generating procedures [such as tracheal intubation or bronchoscopy], or with inadequate infection control [for example, unrecognized patient infections]), moderate (exposure to coronavirus infections, not meeting criteria for high risk), or low (no care of patients with coronavirus infections) (13). We categorized randomized trials on HCWs and risk for influenza or influenza-like illness as higher risk (inpatient) or lower risk (outpatient).
Quality Assessment
Randomized trials were assessed by using criteria adapted from the U.S. Preventive Services Task Force (14). For observational studies, we noted key limitations of each study, such as potential recall, selection, or participation bias; issues regarding outcome evaluation and analytic methods; and confounding (15, 16).
Data Synthesis and Analysis
Results were synthesized narratively. For cluster randomized trials, risk estimates adjusted for cluster effects were presented when available (17). For observational studies, unadjusted and adjusted risk estimates were presented. Quantitative synthesis was not done owing to methodological limitations; study design variability; and heterogeneity in populations, comparisons, and analytical methods. We created an evidence map showing the strength of evidence and effect direction by setting and infection type. The strength of evidence was classified as high, moderate, low, or insufficient, on the basis of the study design, risk for bias, inconsistency, indirectness, and imprecision (18).
Living Review
This review is being maintained as a living review focusing on key questions 1a and 2 (SARS-CoV-2 and COVID-19), with a planned end date 1 year from initial searches. Surveillance is ongoing, using the same searches as the original review, except dropping searches of preprint servers. Study selection and quality assessment will follow the same processes described, except that observational study quality will be formally assessed by using published criteria (14). New evidence that does not substantively change review conclusions will be briefly summarized on a monthly basis; a major update will be performed when new evidence changes the nature or strength of the conclusions.
Role of the Funding Source
The study was funded under contract HHSA290201500009I, task order 75Q80119F32021, from the AHRQ, U.S. Department of Health and Human Services (HHS). The authors of this manuscript are responsible for its content. Statements in the manuscript do not necessarily represent the official views of or imply endorsement by AHRQ or HHS. Staff at AHRQ developed the key questions and review scope but did not have any role in the selection, assessment, or synthesis of evidence. The AHRQ was not involved in the decision to submit this article for publication.
Results
Thirty-nine studies (33 867 participants), all addressing key question 1, met the inclusion criteria (19–57). Figure 1 summarizes the study selection process and number of included studies, by setting (community or health care) and study type. Twelve RCTs (19–21, 23, 24, 28–30, 37, 41, 48, 49) and 3 observational studies (31, 51, 54) were conducted in the community, and 6 RCTs (27, 34, 38–40, 46) and 18 observational studies (22, 25, 26, 32, 33, 35, 36, 42–45, 47, 50, 52, 53, 55–57) were conducted in HCWs (Supplement Tables 3 and 4). There were no RCTs on risk for coronavirus infections. For SARS-CoV-2, there were 2 cohort studies (52, 56). Eighteen observational studies addressed SARS-CoV-1 (25, 26, 31–33, 35, 36, 42–45, 47, 50, 51, 53–55, 57), and 1 cohort study addressed MERS-CoV (22). No death was recorded in any study. The RCTs were usually conducted during influenza season and evaluated the risk for nonspecific clinical respiratory illness, influenza-like illness, and laboratory-confirmed viral respiratory illness. Two Chinese-language studies were translated into English by a native Chinese speaker on the review team (36, 55).
Figure 1. Literature search and selection.
ILI = influenza-like illness; MERS-CoV = Middle East respiratory syndrome coronavirus; SARS-CoV = severe acute respiratory syndrome coronavirus; VRI = viral respiratory illness.
Two RCTs (27, 34) were randomized by individual participant; the remaining trials were randomized by clusters (households, university residence halls, tents during Hajj, hospitals, hospital wards, or outpatient settings). The number of participants ranged from 164 to 7687. The RCTs were conducted during influenza season, except for 2 RCTs of Hajj pilgrims staying in tents (21, 23). Two RCTs (34, 37) reported the incidence of laboratory-confirmed nonpandemic coronavirus infections, but 1 trial only reported 1 case (37). Four trials were conducted in the United States, 1 in Canada, 1 in Australia, 2 in Europe, 2 in Saudi Arabia, and 8 in Asia. Eleven RCTs were rated good-quality, and 7 were rated fair-quality (Supplement Table 5). Limitations of the fair-quality trials included baseline between-group differences and high attrition; one cluster RCT (23) did not adjust for cluster correlation. Blinding of participants to the mask and other interventions (for example, hand hygiene) was not possible.
The observational studies had important limitations (Supplement Table 4). All were retrospective and potentially susceptible to recall bias for determining mask use and other exposures. The studies were limited in their ability to measure and control for the amount and intensity of exposures. Six studies did not control for potential confounders. Of the 15 studies that did control for confounders, only 1 (33) evaluated correlations between masks and other infection control measures (such as gloves, gowns, goggles, or handwashing) to inform variable selection for model building. In the other studies that reported results from multivariate models, correlations between infection control measures and potential collinearity were not addressed.
Effectiveness of Masks
Key Question 1a: SARS-CoV-2
Community settings. No study evaluated masks for preventions of SARS-CoV-2 infections in community settings.
Health care settings. Two cohort studies evaluated mask use and risk for SARS-CoV-2 infection, but had important limitations (52, 56). One study (493 participants) of HCWs in higher- and lower-risk hospital units found N95 respirators to be associated with decreased infection risk versus no mask, but mask use was based on whether the HCW worked in a department in which masks were used, not on assessment of individual use (52). In addition, departments with N95 respirator use differed from departments that did not use N95 respirators in other infection control measures (such as handwashing and use of protective clothing) and exposure to patients with COVID-19. There were also few HCW cases and serious imprecision. The other study was small (37 participants) and evaluated HCWs with inadequate personal protective equipment during exposure to a patient with unrecognized SARS-CoV-2 infection (56). It reported 3 cases of SARS-CoV-2 infection in HCWs, resulting in very imprecise estimates.
Key Question 1b: SARS-CoV-1 and MERS-CoV
Community settings. Three observational studies (2857 participants) evaluated masks and SARS-1 risk in community settings (Supplement Table 4) (31, 51, 54). The studies did not compare mask types or provide details regarding mask type. Wearing a mask was associated with decreased risk for infection in persons without known SARS-1 contacts in 1 study (54) and in household contacts of patients with SARS-1 in 2 studies (Supplement Table 6) (31, 51).
Health care settings. Fifteen observational studies (3994 participants) evaluated the association between mask use by HCWs and risk for SARS-CoV-1 infection (25, 26, 32, 33, 35, 36, 42–45, 47, 50, 53, 55, 57), and 1 study (283 participants) (22) evaluated the association between mask use and MERS-CoV infection (Supplement Table 4). Five studies were conducted in high-risk settings, and the remainder in moderate-risk settings (Supplement Table 7); no study was low risk. The proportion of HCWs with close or direct contact with SARS-CoV-1 or MERS-CoV cases was high in studies that reported this information; use of personal protective equipment varied (Supplement Table 7).
Five observational studies (1208 participants) consistently found N95 respirators to be associated with decreased risk for SARS-CoV-1 infection versus surgical masks (sometimes described as “disposable” masks) in HCWs (Supplement Table 8) (25, 33, 35, 45, 57); all but 1 study (33) were conducted in high-risk settings. Results of 3 comparisons (1207 participants) involving an N95 respirator or surgical versus cloth mask and risk for SARS-CoV-1 in moderate-risk settings were somewhat inconsistent (33, 36, 55). The cloth mask material was cotton or not reported, and cloth masks were described as 12- or 16-layer masks, potentially reducing generalizability to the United States and other countries where cloth masks typically have far fewer layers.
Twelve observational studies (2998 participants) consistently found mask use associated with decreased risk for SARS-CoV-1 infection versus no use (Supplement Table 8) (33, 35, 36, 42–45, 47, 50, 53, 55, 57); of these, 8 specifically evaluated N95 respirators or surgical masks (33, 35, 36, 45, 47, 50, 55, 57). Results were consistent when studies were stratified by high- or moderate-risk setting (34, 45, 53, 57). Masks were associated with decreased risk for SARS-CoV-1 infection in multivariate models in 5 studies (33, 43, 47, 50, 55).
Four studies (626 participants) found more consistent mask use by HCWs to be associated with decreased risk for SARS-CoV-1 or MERS-CoV infection versus less consistent use (Supplement Table 8) (22, 32, 35, 43); of these, 3 specifically evaluated N95 or surgical masks (22, 32, 35) and 1 was in a high-risk setting (32). In 1 of the studies, consistent use of N95 respirators or surgical masks was associated with decreased infection risk in HCWs who had direct contact with SARS-1 patients, direct contact with non–SARS-1 patients, and no direct patient contact (32).
Key Question 1c: Influenza, Influenza-like Illness, and Other Viral Respiratory Illness
Community settings. Twelve RCTs (16 836 participants) evaluated masks in community settings (Table 1 and Supplement Table 3) (19–21, 23, 24, 28–30, 37, 41, 48, 49). The settings were households, university residence halls, and tents used by Hajj pilgrims. Masks were used by infected index cases (“source control”), household contacts of index cases, cases and contacts, or persons without specific contact with cases. All participants generally received education on preventing respiratory infection and hand hygiene. All of the trials compared a mask versus no mask; 1 trial also compared a mask versus a mask plus handwashing training (48).
Only 1 RCT (290 participants) directly compared different mask types (37). It evaluated a P2 mask (Australian equivalent to an N95 respirator) versus a surgical mask in adult household contacts of children with influenza-like illness. There were no differences between either mask type versus no mask in infection outcomes, though estimates were imprecise. The RCT did not report cluster-adjusted risk estimate for the P2 versus the surgical mask, but the calculated (crude) unadjusted estimate was not statistically significant. Adherence to mask use was low, potentially reducing effectiveness (Supplement Table 9). In a multivariate analysis, adherence to either mask was associated with decreased risk for influenza-like illness (hazard ratio, 0.26 to 0.32).
Eight trials (6510 participants), including the trial described above, evaluated use of surgical masks within households with an influenza or influenza-like illness index case (child or adult) (24, 28–30, 37, 41, 48, 49). Compared with no masks, surgical masks were not associated with decreased risk for clinical respiratory illness, influenza-like illness, or laboratory-confirmed viral illness in household contacts when masks were worn by household contacts (30, 37, 48), index cases (24, 41), or both (28, 29, 49). However, some estimates were imprecise, mask-wearing adherence was limited (Supplement Table 9), and some crossover occurred. Two trials found no differences between surgical masks plus handwashing versus handwashing alone in risk for infections in household contacts of index cases (30, 48).
Two trials (2475 participants) of students living in university residence halls without specific contacts with cases also found no significant differences between a surgical mask versus no mask and risk for influenza-like illness (19, 20). Two trials (7851 participants) found that surgical masks, compared with no masks, were not associated with decreased risk for infections in Hajj pilgrims with or without an infected index case within the same tent (21, 23).
Health care settings. Six RCTs (9411 participants) evaluated mask use among HCWs in health care settings (Table 2 and Supplement Table 3) (27, 34, 38–40, 46). One was a pilot trial that reported adherence and harms but not effects on risk for infections (27). Of the other 5 trials, 4 compared an N95 respirator versus surgical mask (38–40, 46) and 1 (38) compared a surgical versus cloth mask (Table 2). Masks were generally used in addition to handwashing, though details on use of personal protective equipment (for example, eye protection, gowns, and gloves) were limited.
Three RCTs (3532 participants) compared N95 respirators versus surgical masks in higher-risk settings (such as emergency departments, respiratory wards, pediatric wards, and intensive care units) (34, 39, 40). One trial (422 participants) found both N95 respirators and surgical masks to be associated with a very similar likelihood of a physician visit for acute respiratory illness (6.2% vs. 6.1%) (34). Two trials (3110 participants) found an N95 respirator to be associated with decreased risk for clinical respiratory illness, with absolute differences that ranged from –2.8% to –7.7% (39, 40).
In all 3 trials, there were few cases of influenza-like illness, resulting in imprecise estimates (34, 39, 40). For laboratory-confirmed viral respiratory infections, 1 trial (34) that did not require HCWs to have symptoms found no difference between an N95 respirator and a surgical mask in infection risk. In the other 2 trials, only symptomatic laboratory-confirmed viral respiratory infections were diagnosed; the number of cases was small, and estimates were imprecise. One trial reported no difference in the subgroup of laboratory-confirmed (not necessarily symptomatic) viral infections by nonpandemic coronaviruses but was underpowered for this outcome, with a total of 21 cases (34). The other 2 trials did not report nonpandemic coronavirus infections.
Two trials described above included 2 N95 respirator groups (39, 40). One trial found that the effects of an N95 respirator versus surgical mask on clinical respiratory illness were similar for fit-tested and non–fit-tested N95 respirators (4.6% vs. 3.3%) (39). The other trial found continuous use (at all times while working) of an N95 respirator to be associated with a small decrease in clinical respiratory illness risk versus intermittent use (only during high-risk procedures or barrier situations) of an N95 respirator (7.2% vs. 11.8%) (40).
One trial (1868 participants) of HCWs in higher-risk settings found a surgical mask to be associated with decreased risk for clinical respiratory illness, influenza-like illness, and laboratory-confirmed viral infections versus cloth masks, but estimates were imprecise and not statistically significant (38).
One trial of HCWs (2862 participants) in lower-risk outpatient settings found no differences between an N95 respirator and a surgical mask in risk for clinical respiratory illness, influenza-like illness, laboratory-confirmed viral illness, or laboratory-confirmed influenza (46).
Harms
Reporting of harms in the RCTs was suboptimal but did not indicate serious harms with mask use (Supplement Table 9). When reported, the most common adverse events were discomfort, breathing difficulties, and skin events. One trial found use of an N95 respirator to be associated with increased risk for headache and breathing difficulty compared with a surgical mask in HCWs (39), but 1 trial found no difference between a P2 mask (N95 respirator equivalent) versus surgical mask in adverse events in persons in the community (37). One trial reported no differences in harms between a surgical versus cloth mask in HCWs (38).
Discussion
This rapid, living review summarizes the evidence on the comparative effectiveness and effectiveness for preventing coronavirus and other respiratory infections. Figure 2 is an evidence map summarizing the strength of evidence for key comparisons by setting and infection type (Supplement Table 10). The map shows that direct evidence on the comparative effectiveness of masks for preventing COVID-19 due to SARS-CoV-2 infection is lacking. Therefore, it was necessary to also consider evidence for other respiratory infections, though the applicability to COVID-19 is uncertain. In addition, the strength of evidence varied from moderate to insufficient; no comparison was graded high strength of evidence.
Figure 2. Masks for prevention of respiratory virus infection: evidence map.
ILI = influenza-like illness; MERS-CoV = Middle East respiratory syndrome coronavirus; RCT = randomized controlled trial; SARS-CoV = severe acute respiratory syndrome coronavirus; VRI = viral respiratory illness.
* Only observational evidence was included for these infections.
† Only RCT evidence was included for these infections.
‡ N95 respirator or equivalent (for example, P2 mask).
In community settings, one RCT found no difference between N95 or equivalent respirators versus surgical masks in risk for noncoronavirus respiratory illness (37). The RCTs in community settings, typically conducted during influenza seasons, also did not indicate effectiveness of mask use versus no mask use for reducing viral respiratory infection risk, though mask compliance was suboptimal. Observational data on mask use effectiveness in community settings for preventing infections associated with epidemic coronaviruses were limited but suggest possible reduced risk for SARS-1. The difference in findings could be related to higher mask compliance in pandemic outbreak settings, greater effectiveness of masks for SARS-1, or residual confounding.
In HCWs, observational studies suggest that N95 masks might be associated with decreased risk for SARS-CoV-1 infection compared with surgical masks, and mask use in general appears to be associated with decreased risk for SARS-CoV-1 infection. All studies were conducted in high- or moderate-risk settings, with uncertain applicability to low-risk settings (those without direct care of infected patients). Review of RCTs indicates that N95 respirators and surgical masks are probably associated with similar risk for influenza-like illness and laboratory-confirmed viral infections in high- and low-risk settings. However, there was some inconsistency in effects of N95 respirators versus surgical masks on clinical respiratory infections in high-risk settings, with 1 trial (34) showing no difference in physician visits for respiratory illness and 2 trials (39, 40) showing N95 respirators to be associated with a small decrease in risk. The only trial comparing N95 respirators versus surgical masks in a low-risk (primary care) setting found no difference in risk for clinical respiratory illness (46). There was no evidence to address effects of extended use or reuse of N95 respirators on infection risk; evidence on nonclinical outcomes (for example, measures of filtration, contamination, and mask failure) is summarized elsewhere (5).
Our findings are generally consistent with those of recent systematic reviews on mask use in community and health care settings that found N95 respirators and surgical masks to be associated with similar risk for influenza and influenza-like illness (58–62). It differs from prior reviews by considering both randomized trials and observational studies, evaluating mask use in community and health care settings, considering harms, comparing effects of consistent versus less consistent mask use, and including a more comprehensive set of relevant studies. We also implemented living review processes in order to incorporate new evidence on an ongoing basis. There was some overlap between this review and our living review on risk factors (including various types of personal protective equipment) for coronavirus infections in HCWs (12). This review differed from our prior review by including studies conducted in community settings, focusing on mask use, and including effects on noncoronavirus viral respiratory infections.
The evidence base has important limitations. As noted, the evidence on mask use and risk for SARS-CoV-2 infection is very sparse. In randomized trials, adherence to mask use was suboptimal, potentially reducing estimates of effectiveness compared with use during pandemic outbreaks, when adherence may be higher. Observational studies were retrospective, were susceptible to recall bias and confounding, and did not address correlations between mask use and other infection prevention and control measures. Applicability of evidence on masks and risk for SARS-CoV-1, MERS-CoV, and other viral respiratory illness to SARS-CoV-2 is uncertain. The applicability of evidence on influenza and influenza-like illnesses to SARS-CoV-2 could be reduced owing to differential transmission dynamics, lower mask adherence, or limited use of other personal protective equipment (63).
The review process had limitations. In particular, we used streamlined rapid review methods for searching and selecting studies. We did not perform critical appraisal of observational studies by using a formal instrument, though key methodological limitations were highlighted. We included 1 non–peer-reviewed study (21), which could reduce data quality. Meta-analysis was not attempted owing to study limitations and heterogeneity in study designs, comparisons, and analyses.
Research is urgently needed to clarify the comparative effectiveness of masks for transmission of COVID-19 in community and health care settings; randomized trials are in progress (64, 65). Observational studies that prospectively measure mask use, other infection prevention and control measures (accounting for potential correlations), and exposures could supplement randomized trials. Given limitations in the supply of N95 respirators, understanding the effects of reuse or extended use of N95 respirators is a priority (66).
In conclusion, evidence on the effectiveness of masks for prevention of respiratory infection is stronger in health care than community settings. Use of N95 respirators might reduce SARS-CoV-1 risk versus surgical masks in health care settings, but applicability to SARS-CoV-2 is uncertain.
Supplemental Material
References
1.
Wilson NM, Norton A, Young FP, et al. Airborne transmission of severe acute respiratory syndrome coronavirus-2 to healthcare workers: a narrative review. Anaesthesia. 2020. [PMID: 32311771] doi: 10.1111/anae.15093
2.
Bach M. Understanding respiratory protection options in healthcare: the overlooked elastomeric. NIOSH Science Blog. Centers for Disease Control and Prevention. 6 July 2017. Accessed at https://blogs.cdc.gov/niosh-science-blog/2017/07/06/elastomerics on 5 May 2020.
3.
Centers for Disease Control and Prevention. Interim infection prevention and control recommendations for patients with suspected or confirmed coronavirus disease 2019 (COVID-19) in healthcare settings. 12 April 2020. Accessed at www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control-recommendations.html on 15 April 2020.
4.
World Health Organization. Shortage of personal protective equipment endangering health workers worldwide. 3 March 2020. Accessed at www.who.int/news-room/detail/03-03-2020-shortage-of-personal-protective-equipment-endangering-health-workers-worldwide on 15 April 2020.
5.
ECRI. Clinical evidence assessment: safety of extended use and reuse of N95 respirators. March 2020. Accessed at https://assets.ecri.org/PDF/COVID-19-Resource-Center/COVID-19-Clinical-Care/COVID-ECRI-N95-Respirators-updated.pdf on 10 April 2020.
6.
Centers for Disease Control and Prevention. Decontamination and reuse of filtering facepiece respirators. 2020. Accessed at www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html on 15 April 2020.
7.
Chou R, Dana T, Jungbauer R, et al. Masks for Prevention of COVID-19 in Community and Healthcare Settings: A Living Rapid Review. Rapid Evidence Product. (Prepared by the Pacific Northwest Evidence-based Practice Center under contract no. 290-2015-00009-I.) AHRQ publication no. 20-EHC016. Agency for Healthcare Research and Quality. June 2020. doi: 10.23970/AHRQEPCCOVIDMASKS
8.
Haby MM, Chapman E, Clark R, et al. What are the best methodologies for rapid reviews of the research evidence for evidence-informed decision making in health policy and practice: a rapid review. Health Res Policy Syst. 2016;14:83. [PMID: 27884208]
9.
Elliott JH, Synnot A, Turner T, et al; Living Systematic Review Network. Living systematic review: 1. Introduction—the why, what, when, and how. J Clin Epidemiol. 2017;91:23-30. [PMID: 28912002] doi: 10.1016/j.jclinepi.2017.08.010
10.
World Health Organization. Global research on coronavirus disease (COVID-19). 2020. Accessed at www.who.int/emergencies/diseases/novel-coronavirus-2019/global-research-on-novel-coronavirus-2019-ncov on 30 March 2020.
11.
Cold Spring Harbor Laboratory. medRxiv: the preprint server of health sciences. 2020. Accessed at www.medrxiv.org on 30 March 2020.
12.
Chou R, Dana T, Buckley DI, et al. Epidemiology of and risk factors for coronavirus infection in health care workers. A living rapid review. Ann Intern Med. 2020;173:120-36. [PMID: 32369541]. doi: 10.7326/M20-1632
13.
Centers for Disease Control and Prevention. Interim U.S. guidance for risk assessment and work restrictions for healthcare personnel with potential exposure to COVID-19. 29 May 2020. Accessed at www.cdc.gov/coronavirus/2019-ncov/hcp/guidance-risk-assesment-hcp.html on 6 June 2020.
14.
U.S. Preventive Services Task Force. Procedure manual appendix VI. Criteria for assessing internal validity of individual studies. 2017. Accessed at www.uspreventiveservicestaskforce.org/uspstf/procedure-manual-appendix-vi-criteria-assessing-internal-validity-individual-studies on 14 June 2020.
15.
Centre for Research Synthesis and Decision Analysis, University of Bristol. The ROBINS-E tool (Risk Of Bias In Non-randomized Studies—of Exposures). 2020. Accessed at www.bristol.ac.uk/population-health-sciences/centres/cresyda/barr/riskofbias/robins-e on 30 March 2020.
16.
Wells GA, Shea B, O’Connell D, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. 2019. Accessed at www.ohri.ca/programs/clinical_epidemiology/oxford.asp on 30 March 2020.
17.
Campbell MK, Grimshaw JM, Elbourne DR. Intracluster correlation coefficients in cluster randomized trials: empirical insights into how should they be reported. BMC Med Res Methodol. 2004;4:9. [PMID: 15115554]
18.
Berkman ND, Lohr KN, Ansari MT, et al. Grading the strength of a body of evidence when assessing health care interventions: an EPC update. J Clin Epidemiol. 2015;68:1312-1324. [PMID: 25721570] doi: 10.1016/j.jclinepi.2014.11.023
19.
Aiello AE, Murray GF, Perez V, et al. Mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial. J Infect Dis. 2010;201:491-498. [PMID: 20088690] doi: 10.1086/650396
20.
Aiello AE, Perez V, Coulborn RM, et al. Facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial. PLoS One. 2012;7:e29744. [PMID: 22295066] doi: 10.1371/journal.pone.0029744
21.
Alfelali M, Haworth EA, Barasheed O, et al. Facemask versus no facemask in preventing viral respiratory infections during Hajj: a cluster randomised open label trial. SSRN. Preprint posted online 11 March 2019.
22.
Alraddadi BM, Al-Salmi HS, Jacobs-Slifka K, et al. Risk factors for Middle East respiratory syndrome coronavirus infection among healthcare personnel. Emerg Infect Dis. 2016;22:1915-1920. [PMID: 27767011] doi: 10.3201/eid2211.160920
23.
Barasheed O, Almasri N, Badahdah AM, et al; Hajj Research Team. Pilot randomised controlled trial to test effectiveness of facemasks in preventing influenza-like illness transmission among Australian Hajj pilgrims in 2011. Infect Disord Drug Targets. 2014;14:110-116. [PMID: 25336079]
24.
Canini L, Andréoletti L, Ferrari P, et al. Surgical mask to prevent influenza transmission in households: a cluster randomized trial. PLoS One. 2010;5:e13998. [PMID: 21103330] doi: 10.1371/journal.pone.0013998
25.
Caputo KM, Byrick R, Chapman MG, et al. Intubation of SARS patients: infection and perspectives of healthcare workers. Can J Anaesth. 2006;53:122-129. [PMID: 16434750]
26.
Chen WQ, Ling WH, Lu CY, et al. Which preventive measures might protect health care workers from SARS? BMC Public Health. 2009;9:81. [PMID: 19284644] doi: 10.1186/1471-2458-9-81
27.
Chughtai AA, Seale H, Dung TC, et al. Compliance with the use of medical and cloth masks among healthcare workers in Vietnam. Ann Occup Hyg. 2016;60:619-630. [PMID: 26980847] doi: 10.1093/annhyg/mew008
28.
Cowling BJ, Chan KH, Fang VJ, et al. Facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial. Ann Intern Med. 2009;151:437-446. [PMID: 19652172]
29.
Cowling BJ, Fung RO, Cheng CK, et al. Preliminary findings of a randomized trial of non-pharmaceutical interventions to prevent influenza transmission in households. PLoS One. 2008;3:e2101. [PMID: 18461182] doi: 10.1371/journal.pone.0002101
30.
Larson EL, Ferng YH, Wong-McLoughlin J, et al. Impact of non-pharmaceutical interventions on URIs and influenza in crowded, urban households. Public Health Rep. 2010 Mar-Apr;125:178-191. [PMID: 20297744]
31.
Lau JT, Lau M, Kim JH, et al. Probable secondary infections in households of SARS patients in Hong Kong. Emerg Infect Dis. 2004;10:235-243. [PMID: 15030689]
32.
Lau JT, Fung KS, Wong TW, et al. SARS transmission among hospital workers in Hong Kong. Emerg Infect Dis. 2004;10:280-286. [PMID: 15030698]
33.
Jia N, Feng D, Fang LQ, et al. Case fatality of SARS in mainland China and associated risk factors. Trop Med Int Health. 2009;14 Suppl 1:21-27. [PMID: 19508439] doi: 10.1111/j.1365-3156.2008.02147.x
34.
Loeb M, Dafoe N, Mahony J, et al. Surgical mask vs N95 respirator for preventing influenza among health care workers: a randomized trial. JAMA. 2009;302:1865-1871. [PMID: 19797474] doi: 10.1001/jama.2009.1466
35.
Loeb M, McGeer A, Henry B, et al. SARS among critical care nurses, Toronto. Emerg Infect Dis. 2004;10:251-255. [PMID: 15030692]
36.
Ma HJ, Wang HW, Fang LQ, et al. [A case-control study on the risk factors of severe acute respiratory syndromes among health care workers]. Zhonghua Liu Xing Bing Xue Za Zhi. 2004;25:741-744. [PMID: 15555351]
37.
MacIntyre CR, Cauchemez S, Dwyer DE, et al. Face mask use and control of respiratory virus transmission in households. Emerg Infect Dis. 2009;15:233-241. [PMID: 19193267]
38.
MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open. 2015;5:e006577. [PMID: 25903751] doi: 10.1136/bmjopen-2014-006577
39.
MacIntyre CR, Wang Q, Cauchemez S, et al. A cluster randomized clinical trial comparing fit-tested and non-fit-tested N95 respirators to medical masks to prevent respiratory virus infection in health care workers. Influenza Other Respir Viruses. 2011;5:170-179. [PMID: 21477136] doi: 10.1111/j.1750-2659.2011.00198.x
40.
MacIntyre CR, Wang Q, Seale H, et al. A randomized clinical trial of three options for N95 respirators and medical masks in health workers. Am J Respir Crit Care Med. 2013;187:960-966. [PMID: 23413265] doi: 10.1164/rccm.201207-1164OC
41.
MacIntyre CR, Zhang Y, Chughtai AA, et al. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness. BMJ Open. 2016;6:e012330. [PMID: 28039289] doi: 10.1136/bmjopen-2016-012330
42.
Nishiura H, Kuratsuji T, Quy T, et al. Rapid awareness and transmission of severe acute respiratory syndrome in Hanoi French Hospital, Vietnam. Am J Trop Med Hyg. 2005;73:17-25. [PMID: 16014825]
43.
Nishiyama A, Wakasugi N, Kirikae T, et al. Risk factors for SARS infection within hospitals in Hanoi, Vietnam. Jpn J Infect Dis. 2008;61:388-390. [PMID: 18806349]
44.
Pei LY, Gao ZC, Yang Z, et al. Investigation of the influencing factors on severe acute respiratory syndrome among health care workers. Beijing Da Xue Xue Bao Yi Xue Ban. 2006;38:271-275. [PMID: 16778970]
45.
Raboud J, Shigayeva A, McGeer A, et al. Risk factors for SARS transmission from patients requiring intubation: a multicentre investigation in Toronto, Canada. PLoS One. 2010;5:e10717. [PMID: 20502660] doi: 10.1371/journal.pone.0010717
46.
Radonovich LJ Jr, Simberkoff MS, Bessesen MT, et al; ResPECT investigators. N95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial. JAMA. 2019;322:824-833. [PMID: 31479137] doi: 10.1001/jama.2019.11645
47.
Seto WH, Tsang D, Yung RW, et al; Advisors of Expert SARS group of Hospital Authority. Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS). Lancet. 2003;361:1519-1520. [PMID: 12737864]
48.
Simmerman JM, Suntarattiwong P, Levy J, et al. Findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in Bangkok, Thailand. Influenza Other Respir Viruses. 2011;5:256-267. [PMID: 21651736] doi: 10.1111/j.1750-2659.2011.00205.x
49.
Suess T, Remschmidt C, Schink SB, et al. The role of facemasks and hand hygiene in the prevention of influenza transmission in households: results from a cluster randomised trial; Berlin, Germany, 2009-2011. BMC Infect Dis. 2012;12:26. [PMID: 22280120] doi: 10.1186/1471-2334-12-26
50.
Teleman MD, Boudville IC, Heng BH, et al. Factors associated with transmission of severe acute respiratory syndrome among health-care workers in Singapore. Epidemiol Infect. 2004;132:797-803. [PMID: 15473141]
51.
Tuan PA, Horby P, Dinh PN, et al; WHO SARS Investigation Team in Vietnam. SARS transmission in Vietnam outside of the health-care setting. Epidemiol Infect. 2007;135:392-401. [PMID: 16870029]
52.
Wang X, Pan Z, Cheng Z. Association between 2019-nCoV transmission and N95 respirator use [Letter]. J Hosp Infect. 2020;105:104-105. [PMID: 32142885] doi: 10.1016/j.jhin.2020.02.021
53.
Wilder-Smith A, Teleman MD, Heng BH, et al. Asymptomatic SARS coronavirus infection among healthcare workers, Singapore. Emerg Infect Dis. 2005;11:1142-1145. [PMID: 16022801]
54.
Wu J, Xu F, Zhou W, et al. Risk factors for SARS among persons without known contact with SARS patients, Beijing, China. Emerg Infect Dis. 2004;10:210-216. [PMID: 15030685]
55.
Yin WW, Gao LD, Lin WS, et al. [Effectiveness of personal protective measures in prevention of nosocomial transmission of severe acute respiratory syndrome]. Zhonghua Liu Xing Bing Xue Za Zhi. 2004;25:18-22. [PMID: 15061941]
56.
Heinzerling A, Stuckey MJ, Scheuer T, et al. Transmission of COVID-19 to health care personnel during exposures to a hospitalized patient—Solano County, California, February 2020. MMWR Morb Mortal Wkly Rep. 2020;69:472-476. [PMID: 32298249] doi: 10.15585/mmwr.mm6915e5
57.
Scales DC, Green K, Chan AK, et al. Illness in intensive care staff after brief exposure to severe acute respiratory syndrome. Emerg Infect Dis. 2003;9:1205-1210. [PMID: 14609453]
58.
MacIntyre CR, Chughtai AA. A rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients. Int J Nurs Stud. 2020;108:103629. [PMID: 32512240] doi: 10.1016/j.ijnurstu.2020.103629
59.
Brainard JS, Jones N, Lake I, et al. Facemasks and similar barriers to prevent respiratory illness such as COVID-19: a rapid systematic review. medRxiv. Preprint posted online 6 April 2020. doi: 10.1101/2020.04.01.20049528
60.
Long Y, Hu T, Liu L, et al. Effectiveness of N95 respirators versus surgical masks against influenza: a systematic review and meta-analysis. J Evid Based Med. 2020;13:93-101. [PMID: 32167245] doi: 10.1111/jebm.12381
61.
Bartoszko JJ, Farooqi MAM, Alhazzani W, et al. Medical masks vs N95 respirators for preventing COVID-19 in healthcare workers: a systematic review and meta-analysis of randomized trials. Influenza Other Respir Viruses. 2020. [PMID: 32246890] doi: 10.1111/irv.12745
62.
Jefferson T, Jones M, Al Ansari LA, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Part 1—face masks, eye protection and person distancing: systematic review and meta-analysis. medRxiv. Preprint posted online 7 April 2020. doi: 10.1101/2020.03.30.20047217
63.
Bridges CB, Kuehnert MJ, Hall CB. Transmission of influenza: implications for control in health care settings. Clin Infect Dis. 2003;37:1094-1101. [PMID: 14523774] doi: 10.1086/378292
64.
Medical masks vs N95 respirators for COVID-19. ClinicalTrials.gov: NCT04296643. Accessed at https://ClinicalTrials.gov/show/NCT04296643 on 14 June 2020.
65.
Reduction in COVID-19 infection using surgical facial masks outside the healthcare system. ClinicalTrials.gov: NCT04337541. Accessed at https://ClinicalTrials.gov/show/NCT04337541 on 14 June 2020.
66.
Ranney ML, Griffeth V, Jha AK. Critical supply shortages—the need for ventilators and personal protective equipment during the COVID-19 pandemic. N Engl J Med. 2020;382:e41. [PMID: 32212516] doi: 10.1056/NEJMp2006141
Information & Authors
Information
Published In
Annals of Internal Medicine
Volume 173 • Number 7 • 6 October 2020
Pages: 542 - 555
History
Published online: 24 June 2020
Published in issue: 6 October 2020
Keywords
Authors
Metrics & Citations
Metrics
Citations
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. For an editable text file, please select Medlars format which will download as a .txt file. Simply select your manager software from the list below and click Download.
For more information or tips please see 'Downloading to a citation manager' in the Help menu.
Download article citation data for:
Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings: A Living Rapid Review. Ann Intern Med.2020;173:542-555. [Epub 24 June 2020]. doi:10.7326/M20-3213
Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings: A Living Rapid Review. Ann Intern Med.2020;173:542-555. [Epub 24 June 2020]. doi:10.7326/M20-3213
View More
Get Access
Login Options:
Purchase
You will be redirected to acponline.org to sign-in to Annals to complete your purchase.
Create your Free Account
You will be redirected to acponline.org to create an account that will provide access to Annals.
Update Alert: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings
This is the first monthly update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings (1). Searches were updated from 2 June 2020 to 2 July 2020, using the same search strategies as the original review. The update searches identified 321 citations. Due to the high volume of literature and to focus on higher-quality evidence, we modified selection criteria for this and future updates by restricting inclusion to peer-reviewed studies. Other inclusion criteria were unchanged. One study on the prevention of SARS-CoV-2 infection in a community setting was added for this update (2).
The original rapid review included 39 studies of mask use for the prevention of viral illness. No studies in the original review assessed the effect of mask use on prevention of SARS-CoV-2 in the community, and 2 observational studies reporting on mask use in health care settings for SARS-CoV-2 prevention had methodological limitations.
The new study added for this update was a retrospective cohort study of 124 households with an index SARS-CoV-2 case and 355 uninfected household contacts (Supplement Table 1) (2). Households in which masks were used by at least 1 family member (including the index case) before the development of symptoms by the index case were associated with decreased risk for incident infections, after adjustment for other hygiene and infection control practices, physical distance to index case, environmental factors, and presence of diarrhea in the index case (adjusted odds ratio, 0.21 [95% CI, 0.06 to 0.79]) (Supplement Table 2).
There was no association between mask use after illness onset in the index case and risk for SARS-CoV-2 infections in family members. Masks could be N95 respirators, surgical masks, or cloth face coverings, and the study did not conduct analyses by specific mask type. The study was susceptible to recall bias; in addition, the analysis used households (rather than exposed individuals) as the unit of analysis and did not analyze mask use by the index case (“source control”) separately from mask use by household contacts (Supplement Table 3). Therefore, although the new study provides evidence regarding the effectiveness of masks in community settings for prevention of SARS-CoV-2 infection, the strength of evidence is insufficient (Supplement Table 4).
No new studies evaluated the effects of mask use and risk for SARS-CoV-2 infection in health care settings or effects of mask use and risk for SARS-CoV-1 infection, MERS-CoV infection, or influenza or influenza-like illness. There were no new studies on the effectiveness and safety or mask reuse or extended use.
This article was published at Annals.org on 20 July 2020.
References
1. Chou R, Dana T, Jungbauer R, et al. Masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings: a living rapid review. Ann Intern Med. 2020. [PMID: 32579379] doi:10.7326/M20-3213
2. Wang Y, Tian H, Zhang L, et al. Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China. BMJ Glob Health. 2020;5. [PMID: 32467353] doi:10.1136/bmjgh-2020-002794
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L20-0948.
Update Alert 2: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings
This is the second monthly update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in health care and community settings (1). Searches were updated from 3 July 2020 to 2 August 2020 using the same search strategies as the original review, except that inclusion was restricted to peer-reviewed studies. The update searches identified 286 citations. One study on masks for prevention of SARS-CoV-2 infection in a health care setting was added for this update ( Supplement ) (2); the original review and prior update had no studies on masks for prevention of SARS-CoV-2 infection.
The new case–control study was done in India. It evaluated 378 health care workers infected with SARS-CoV-2 and 373 uninfected health care worker controls using data drawn from a national database registry of health care workers undergoing SARS-CoV-2 testing (2). The study found that any mask use (mask type not specified) was associated with a lower risk for SARS-CoV-2 infection compared with no mask use (unadjusted odds ratio, 0.35 [95% CI, 0.22 to 0.57]). However, mask use was not retained in the multivariable model. The study was susceptible to recall bias. In addition, 40% of eligible cases were not included in the study and attrition was not reported. Given these limitations, the strength of evidence on mask use versus no use in health care settings and risk for SARS-CoV-2 infection was assessed as insufficient ( Supplement ).
No new studies evaluated the effects of mask use and risk for SARS-CoV-2 infection in community settings or the effects of mask use and risk for SARS-CoV-1 infection, Middle East respiratory syndrome-CoV infection, or influenza or influenza-like illness. There were no new studies on the effectiveness and safety of mask reuse or extended use. We plan the next update in 2 months.
This article was published at Annals.org on 27 August 2020
References
1. Chou R, Dana T, Jungbauer R, et al. Masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. A living rapid review. Ann Intern Med. 2020. [PMID: 32579379] doi:10.7326/M20-3213
2. Chatterjee P, Anand T, Singh KJ, et al. Healthcare workers & SARS-CoV-2 infection in India: a case-control investigation in the time of COVID-19. Indian J Med Res. 2020;151:459-467. [PMID: 32611916] doi:10.4103/ijmr.IJMR_2234_20
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L20-1067.
Update Alert 3: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the third update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings (1). Searches were updated from August 3, 2020 to October 2, 2020, using the same search strategies as the original review. The update searches identified 407 citations. One study (2) on use of masks and SARS-CoV-2 infection in a community setting and two studies (3, 4) in a healthcare setting were added (Appendix Tables 1-3).
The evidence on mask use in community settings and risk of SARS-CoV-2 infection was previously assessed as insufficient, based on one study with methodological limitations (5). A new case-control study in Thailand enrolled asymptomatic contacts of patients with COVID-19 from three large community clusters (211 cases and 839 uninfected controls) (2). Wearing a mask all the time was associated with decreased risk of SARS-CoV-2 infection versus no use after adjusting for age, sex, exposure to contact, sharing of dishes, cups, or cigarettes, and handwashing (adjusted OR 0.23, 95% CI 0.09 to 0.60), but inconsistent use was not associated with decreased risk (adjusted OR 0.87, 95% CI 0.41 to 1.84). Mask type (medical mask only, non-medical mask only, or both) was not independently associated with risk of SARS-CoV-2 infection (p=0.54). Methodological limitations included potential recall bias; in addition, there was missing data, control for exposures was limited, and there were potential data discrepancies. Therefore, the strength of evidence for mask use and risk of SARS-CoV-2 in community settings remained insufficient (Appendix Table 4).
The evidence on mask use in healthcare settings and risk of SARS-CoV-2 infection was also previously assessed as insufficient, based on one study with methodological limitations (6). Two new studies reported on mask use in healthcare settings (3, 4). One cohort study (n=903) of hospital healthcare workers in Italy exposed to a patient with COVID-19 reported an imprecise estimate with no statistically significant difference between mask use (FFP2-3 [equivalent to N95 or N99] or surgical mask) versus no mask use and risk of COVID-19 infection (adjusted OR 1.6, 95% CI 0.9 to 2.9). Use of an FFP2-3 mask was associated with increased risk of COVID-19 infection compared with a surgical mask (adjusted OR 7.1, 95% 3.0 to 16.7) (4). A case-control study of hospital physicians in Bangladesh (98 COVID-19 cases, 92 controls) also reported an imprecise estimate for a medical mask versus no mask and risk of COVID-19 (adjusted OR 1.40, 95% CI 0.30 to 6.42), though an N95 mask was associated with decreased risk of COVID-19 versus no mask during aerosol-generating procedures (OR 0.37, 0.16 to 0.87) (3). Both studies had serious methodological limitations, including potential recall bias and data discrepancies. In addition, one study (4) only controlled for age and it was unclear what confounders were controlled for in the other study (3). Therefore, evidence for mask use versus nonuse and comparing masks types in healthcare settings remained insufficient (Appendix Table 4).
There were no new studies on the effectiveness and safety or mask reuse or extended use.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L20-1292.
Update Alert 4: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the fourth update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings (1). The first three updates were monthly and the interval was switched to bimonthly for this and subsequent updates. Update searches were conducted from October 3, 2020 to December 2, 2020, using the same search strategies as the original review. The update searches identified 739 citations. One study (2) on use of masks and the prevention of SARS-CoV-2 infection in a community setting and two studies (3, 4) in a healthcare setting were added for this update (Appendix Tables 1-4).
The evidence on any mask use versus no use and surgical mask use versus no use in community settings and risk of SARS-CoV-2 infection was previously assessed as insufficient, based on two (any mask use) or one (surgical mask use) observational studies with methodological limitations (5, 6) A new, good-quality open-label trial of 6,024 community-dwelling adults evaluated effects of a surgical mask worn outside the house in Denmark, at a time when mask-wearing in the community was neither recommended nor common (2). The incidence of SARS-CoV-2 infection among participants (based on a positive IgM or IgG antibody result, positive reverse transcriptase polymerase chain reaction test result, or healthcare diagnosed infection) was 2.0%. Mask use was associated a small, non-statistically significant reduction in risk of SARS-CoV-2 infection versus no mask use (OR 0.82, 95% CI 0.54 to 1.23). Results were consistent in demographic subgroups and when accounting for mask adherence, which was suboptimal. The trial was not designed to assess effects of mask use as source control; in addition, high compliance with other infection control measures (e.g., physical distancing, handwashing) could have attenuated potential benefits. For any mask use versus no use and for surgical use versus no use in community settings, the strength of evidence was changed from insufficient to low for a small reduction in risk of SARS-CoV-2 infection (Appendix Table 5).
The evidence on mask use in healthcare settings and risk of SARS-CoV-2 infection was also previously assessed as insufficient, based on three studies with methodological limitations (7-9). Two new cohort studies, both conducted in the United States, reported on mask use in healthcare settings (3, 4). One study of 16,397 healthcare workers and first responders (86% healthcare workers) found use of an N95 or surgical mask all the time associated with a reduced risk of infection versus use less than all the time (adjusted OR 0.83, 95% CI 0.72 to 0.95 and 0.86, 95% CI 0.75 to 0.98, respectively) (3). In the second study, conducted in 20,614 asymptomatic healthcare workers, risk of infection was reduced with any mask use compared with no mask use (OR 0.58, 95% CI 0.50 to 0.66) (4). Findings were consistent when the analysis was stratified by mask type (N95: OR 0.54, 95% CI 0.47 to 0.62 and surgical masks: OR 0.71, 95% CI 0.58 to 0.86). An N95 was associated with decreased risk versus a surgical mask (OR 0.76, 95% CI 0.63 to 0.92). Both studies had methodological limitations, including potential recall bias. One study (3) did not adjust for confounders and the other (4) only adjusted for age and some inconsistency was present. Therefore, evidence for various comparisons regarding mask use in healthcare settings and risk of SARS-CoV-2 remains insufficient (Appendix Table 5).
As with prior updates, no new studies evaluated the effects of mask use and risk of SARS-CoV-1 infection, MERS-CoV infection, or influenza/influenzalike illness, and there were no new studies on the effectiveness and safety or mask reuse or extended use.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L20-1429.
Update Alert 5: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the fifth update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings (1). The first three updates were monthly and the interval was switched to bimonthly for subsequent updates. Update searches were conducted from December 3, 2020 to February 2, 2021, using the same search strategies as the original review. The update searches identified 613 citations. Two studies (2, 3) on the use of masks and the prevention of SARS-CoV-2 were added for this update: one study (2) conducted in a community setting and one study (3) conducted in a healthcare setting (Appendix Tables 1-3).
Based on evidence from one RCT (4) and two observational studies (5, 6), the strength of evidence for mask use versus non-use for prevention of SARS-CoV-2 in community settings was previously assessed as low for a small reduction in risk of infection with any mask use (Appendix Table 4). One new cross-sectional study conducted in Vermont reported an imprecise estimate for the association between wearing a mask (type unspecified) outside of a work environment and not wearing a mask and SARS-CoV-2 infection risk (OR 2.35, 95% CI 0.67 to 8.25; Appendix Table 3) (2). Mask use was not included in multivariable models; in addition, the study had methodological limitations, including potential selection and recall bias and low participation and SARS-CoV-2 testing rates among eligible participants. Therefore, the strength of evidence for any mask use versus non-use in community settings remains low (Appendix Table 4). Other strength of evidence ratings related to mask use in community settings were unchanged due to no new evidence.
The evidence on various comparisons of mask use in healthcare settings and risk of SARS-CoV-2 infection was previously assessed as insufficient, based on five observational studies with methodological limitations (Appendix Table 4) (7-11). One new study conducted in 500 U.S. hospital workers in a high-prevalence area (SARS-CoV-2 seropositivity: 27%) was added for this update (3). In this study, only two hospital workers reported no mask use. Although the study evaluated N95 only use, surgical mask only use, or N95 and surgical mask use, analyses were of limited usefulness because the comparison group was any other mask use, including other types of masks or non-use (e.g., N95 only use was compared with the combination of surgical mask only, N95 and surgical mask, or no mask use). In addition, estimates were imprecise except for N95 and surgical mask use (OR 0.63, 95% CI 0.41 to 1.0). The comparison of N95 only versus surgical mask only use favored the N95, but the difference was not statistically significant (OR 0.60, 95% CI 0.31 to 1.15). The study had methodological limitations, including no adjustment for confounders and potential recall and selection bias. Based on these limitations and due to inconsistent results across studies, evidence for N95 versus surgical mask use and other comparisons involving mask use and risk of SARS-CoV-2 infection in healthcare settings remains insufficient (Appendix Table 4).
No new studies evaluated the effects of mask use and risk of SARS-CoV-1 infection, MERS-CoV infection, or influenza/influenzalike illness. As with prior updates, there were no studies on the effectiveness and safety or mask reuse or extended use.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M20-3213.
Surveillance Comment
This is the sixth update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. The first 3 updates were monthly, and the interval was switched to bimonthly for subsequent updates. Update searches were done from 3 February to 2 April 2021, using the same search strategies as the original review. The update searches identified 551 citations. No new studies on masks met inclusion criteria.
Update Alert 6: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the seventh update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings (1). The first three updates were monthly and the interval was switched to bimonthly for subsequent updates. The prior update search (through April 2) found no eligible studies. Update searches were conducted from April 3, 2020 to June 2, 2021, using the same search strategies as the original review. The update searches identified 492 citations. Two studies (2, 3) on the use of masks and the prevention of SARS-CoV-2 conducted in a healthcare setting were added for this update; no new studies conducted in a community setting were identified through literature searches (Appendix Tables 1-3).
Based on three observational studies (4-6) comparing N95 respirators with surgical masks for prevention of SARS-CoV-2 in healthcare settings, the strength of evidence was previously assessed as insufficient due to inconsistent effects across studies (Appendix Table 4). One new cross-sectional study conducted in the United States found no significant differences in risk of SARS-CoV-2 seropositivity between N95 respirator and surgical mask use (3). The study had methodological limitations, including potential recall bias and a 50 percent participation. In addition, adjusted risk estimates were not reported. Therefore, the strength of evidence for N95 use versus surgical mask use remains insufficient (Appendix Table 4). Regarding consistency of mask use, the evidence was previously assessed as insufficient based one study that found consistent N95 (adjusted OR 0.83, 95% CI 0.72 to 0.95) or surgical mask (adjusted OR 0.86, 95% CI 0.75 to 0.98) use associated with reduced risk of SARS-CoV-2 infection relative to inconsistent use (7). New evidence from a cross-sectional study conducted in France also found consistent face mask use associated with a reduced risk of SARS-CoV-2 infection testing (adjusted OR 0.07, 95% CI 0.003 to 0.56) compared with inconsistent use (2). Due to inconsistent estimates and few studies, the strength of evidence for consistent mask use and risk of SARS-CoV-2 infection remained insufficient. Other strength of evidence ratings related to mask use in healthcare settings and risk of SARS-CoV-2 infection also remained insufficient (Appendix Table 4)
No new studies evaluated the effects of mask use in a community setting or risk of SARS-CoV-2 infection, MERS-CoV infection, or influenza/influenzalike illness in healthcare workers. In community settings, evidence remains low certainty for an association between any mask use versus no mask use or surgical mask use versus no mask use and decreased risk of SARS-CoV-1 infection. As with prior updates, there were no studies on the effectiveness and safety or mask reuse or extended use.
Given few new eligible studies and little change in conclusions after one year of monthly or bimonthly updates, we will update and re-evaluate the need for continued updates again in six months.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L21-0393.
Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the eighth update alert for a living rapid review (1) on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. The first three updates (2-4) were monthly, after which the interval was switched to bimonthly (5, 6). Following the last update (7), conducted through June 2, 2021, the interval was extended to biannually. For this update, searches were conducted from June 3, 2021 to December 2, 2021, using the same search methods as the original review. Inclusion was restricted to randomized trials and observational studies that controlled for confounders. Non-peer-reviewed studies were excluded unless they were based on data collected after February 2021, when the Delta variant emerged. The update searches identified 1,554 citations. One preprint study (8) conducted in a healthcare setting and six studies (9-14) conducted in a community setting (including one new cluster randomized trial) (9) on masks and SARS-CoV-2 infection met inclusion criteria for this update (Appendix Tables 1-3).
Community settings
One new cluster-randomized trial (9) and five new observational studies (10-14) evaluated the effects of mask use in a community setting and risk of SARS-CoV-2 infection.
In previous updates, the evidence for mask use versus no use for prevention of SARS-CoV-2 infection in community settings was previously assessed as low strength favoring mask use, based on one prior RCT (15) and three observational studies (16-18). The new RCT was a large cluster randomized trial (>340,000 individuals) designed to assess a mask promotion and distribution intervention in Bangladesh (a country with low baseline mask) (Appendix Table 1), with further randomization to surgical or cloth masks along with various other mask promotion interventions (9). Mask promotion intervention villages were associated with decreased symptomatic SARS-CoV-2 seroprevalence (adjusted prevalence ratio 0.90, 95% CI 0.82 to 0.995) and prevalence of WHO COVID-19 symptoms (adjusted prevalence ratio 0.88, 95% CI 0.83 to 0.93) (Appendix Table 5). In an analysis stratified according to mask type, the mask promotion intervention was associated with decreased symptomatic SARS-CoV-2 seroprevalence in surgical mask villages (adjusted prevalence ratio 0.89, 95% CI 0.78 to 0.997), with no difference in cloth mask villages (adjusted prevalence ratio 0.94, 95% CI 0.78 to 1.10). Although no statistical test for a subgroup difference was reported, the confidence intervals of the estimates highly overlapped, suggesting no statistically significant subgroup difference. When stratified by participant age, mask use in surgical mask villages appeared to be most beneficial in those aged 60 years and older, though there was no association between older age and mask effectiveness in the cloth mask villages. The trial was rated fair-quality due to the open-label design, failure to perform serologic testing in 60% of symptomatic participants (though the proportion was similar in intervention and control villages), and differential recruitment (slightly higher in mask promotion intervention compared with no intervention villages). Also, the applicability of findings to settings with higher mask use is uncertain.
Five new observational studies (10-14) also provide evidence on mask use in the community and SARS-CoV-2 infection (Appendix Table 2), though all had methodological limitations, including selection and recall bias, and limited ability to control for potential confounders (Appendix Table 4). The new studies consistently found mask use associated with reduced risk of SARS-CoV-2 infection, with adjusted risk estimates ranging from 0.04 to 0.60 (Appendix Table 5). The new evidence was consistent with the previous findings favoring mask use versus no use, and the evidence was slightly strengthened from low to low-moderate, primarily based on the new RCT (Appendix Table 6). None of the new observational studies compared mask types.
Healthcare settings
Prior updates included four observational studies (19-22) that provided insufficient evidence to determine the effectiveness of N95 (or equivalent) respirators versus surgical masks in healthcare settings (Appendix Table 6); all were conducted prior to the emergence of the Delta variant. One new cohort study (Appendix Table 2) found healthcare workers (HCWs) who primarily used FFP2 (N95 equivalent) masks had decreased risk of SARS-CoV-2 infection (adjusted HR 0.80, 95% CI 0.64 to 1.00) or seroconversion (adjusted OR 0.73, 95% CI 0.53 to 1.00) versus healthcare workers who primarily used surgical masks (Appendix Table 5) (8). In a stratified analysis, the reduction in risk among mostly FFP2 mask users was statistically significant among HCWs with frequent (>20) COVID-19 patient contacts (adjusted hazards ratios 0.66 [95% CI 0.54 to 0.81] for SARS-CoV-2 positive PCR and 0.64 [95% CI 0.42 to 0.97] for seroconversion). The new study had methodological limitations, including potential recall bias, and has not yet undergone peer review; in addition, most data were collected prior to emergence of the Delta variant. Therefore, the strength of evidence comparing N95 respirators with surgical masks for healthcare workers remains insufficient due to methodological limitations, imprecision, and inconsistency across studies (Appendix Table 6).
In summary, new evidence slightly strengthened the evidence of benefit of masks versus no masks in community settings to low-moderate, with no change in insufficient strength of evidence for N95 versus surgical masks in healthcare settings. A final update is planned for six months.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L21-0783.
Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Healthcare and Community Settings
This is the eighth update alert for a living rapid review (1) on the use of masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. The first three updates (2-4) were monthly, after which the interval was switched to bimonthly (5, 6). Beginning in June 2021, the interval was extended to biannually. For this update, searches were conducted from December 3, 2021 to June 2, 2022, using the same search methods as the original review. Inclusion was restricted to randomized trials and observational studies that controlled for confounders. Non-peer-reviewed studies were excluded unless they were based on data collected after February 2021, to capture evidence on mask use in the B.1.617.2 (Delta) and B.1.1.529 (Omicron) variant predominant periods. The update searches identified 1,592 citations. No new RCTs and five new observational studies on the association of mask use and SARS-CoV-2 infection met inclusion criteria (Supplement Table 1). Three studies were conducted in community settings (7-9) and two (10, 11) were conducted in healthcare settings. One preprint study (9) of mask use in community settings collected data during Delta and Omicron predominant periods; the other studies were conducted prior to the emergence of these variants. All studies had methodological limitations, including unclear or low participation rate; potential recall bias; and failure to report attrition or missing data (Supplement Table 2).
Community settings
Three new observational studies (7-9), all conducted in the United States, evaluated the association between mask use in community settings and risk of SARS-CoV-2 infection.
In previous updates, the evidence for mask use versus no use for prevention of SARS-CoV-2 infection in community settings was assessed as low/moderate strength favoring mask use, based on two RCTs (12, 13) and eight observational studies (14-21). For this update, two new observational studies were consistent with prior evidence, finding mask use associated with reduced risk of SARS-CoV-2 infection (Supplement Table 3). The adjusted odds ratio for mask use in public indoor settings versus no use was 0.51 (95% CI 0.29 to 0.93) in one new study (7). The second, non-peer-reviewed study, evaluated mask use for any interaction within a distance of less than sex feet (excluding household members) (9). Wearing a mask for at least one day for such interactions within the preceding 10 days was associated with decreased risk for SARS-CoV-2 infection versus no mask use. The reduction in risk was similar in the pre-Delta (July 2020 to June 2021; adjusted OR 0.60, 95% CI 0.52 to 0.70) and Delta-predominant (July 2021 to November 2021; adjusted OR 0.65, 95% CI 0.53 to 0.81) eras, but attenuated in the Omicron-predominant era (December 2021 to February 2022; adjusted OR 0.86, 95% CI 0.76 to 0.97). Because the new studies were observational and had methodological limitations, the evidence for benefits of mask use versus no use for prevention of SARS-CoV-2 infection in the community remains low/moderate (Supplement Table 4).
One of the new fair quality studies (7) found surgical masks (adjusted OR 0.34, 95% CI 0.13 to 0.90) and N95/KN95 respirators (adjusted OR 0.17, 95% CI 0.05 to 0.64) each associated with reduced risk of SARS-CoV-2 infection versus no mask use (Supplement Table 3). Cloth mask use was also associated with a reduced risk of infection compared with no use, but the estimate was imprecise (adjusted OR 0.44, 95% CI 0.17 to 1.17). The study did not report risk estimates comparing mask types. Based on the adjusted estimates for masks versus no masks provided in the study, we calculated adjusted OR for N95/KN95 respirators versus surgical masks (adjusted OR 0.50, 95% CI 0.10 to 2.48) and surgical vs. cloth masks (adjusted OR 0.77, 95% CI, 0.20 to 3.03); which were imprecise. The correlation among the adjusted ORs was not reported; we assumed correlation=0, resulting in wider confidence intervals than if correlation was present. The new fair quality study provided insufficient evidence for N95 versus surgical mask (no prior studies), and did not change previous assessments (Supplement Table 4) of low strength of evidence for surgical masks versus no masks in community settings (based on two prior RCTs (12, 13) and one observational study (15)), low strength of evidence for no difference between surgical and cloth masks (based on 1 prior RCT (13) and 1 prior observational study (15)), and insufficient evidence for cloth masks versus no masks (based on one prior RCT (13) and one observational study (15)) and N95 respirators versus no masks (no prior studies).
One other new study (8) evaluated the association between adherence to mask use among HCWs when outside of work and risk of SARS-CoV-2 infection, but the estimate was imprecise (for adherence all the time versus most of the time/some of the time/never: adjusted HR 0.8, 95% CI 0.5 to 1.6). The strength of evidence for consistent/always mask use versus inconsistent mask use in the community is insufficient (no prior studies; Supplement Table 4).
Healthcare settings
Two new cohort studies (10, 11) evaluated mask use and risk of SARS-CoV-2 infection in healthcare settings (Supplement Tables 2 and 4). One was a secondary publication (11) for a previously included study (22). In univariate analysis, it found N95 respirator use associated with increased risk of SARS-CoV-2 infection versus non-use (OR 7.8, 95% CI 4.0 to 15.2) (Supplement Table 3), but in multivariate analysis the association between N95 respirator use was not significant enough to be included in the multivariate model (criteria for selecting variables for model not reported); thus the observed univariate association was likely related to confounding due to increased exposures or other factors in HCWs using N95s. The new study did not change the previous assessment of evidence on N95 versus no masks as insufficient (based on three prior studies (23-25)) (Supplement Table 6). One other new study (10) evaluated the association between consistency of mask use and risk of SARS-CoV-2 infection, but the estimate was very imprecise (for mask use at work all/nearly all of the time vs. less than nearly all of the time, adjusted OR 4.0, 95% CI 0.7 to 19.5; Supplement Table 3). Therefore, the evidence on consistency of mask use remains insufficient (Supplement Table 4).
Although this was planned as the final update, a large randomized trial of N95 versus surgical masks (26) has been completed, although results are not yet published. As this trial could impact findings for this comparison, one additional update will be conducted after its publication.
References
Disclosures:
Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L22-0272.