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. Author manuscript; available in PMC: 2023 Feb 4.
Published in final edited form as: Disaster Med Public Health Prep. 2022 Mar 7;17:e96. doi: 10.1017/dmp.2021.369

The effectiveness of mask-wearing on respiratory illness transmission in community settings: a rapid review

Megan Baier 1, Mary Jo Knobloch 1, Fauzia Osman 2, Nasia Safdar 1,2,3
PMCID: PMC9623601  NIHMSID: NIHMS1766409  PMID: 35249589

Abstract

Objective:

Respiratory illnesses, including COVID-19, have resulted in millions of deaths globally. Guidance on mask-wearing in community settings has been inconsistent. This review examined the effectiveness of mask-wearing on respiratory virus transmission in community settings.

Methods:

A search was conducted for English language reports of randomized controlled trials of mask-wearing in the community and effect on laboratory-confirmed respiratory infections or influenza-like-illness. Investigators abstracted study characteristics and assessed bias. Meta-analysis was conducted to calculate pooled risk estimates.

Results:

Eleven studies were included. In 7 studies that evaluated influenza-like-illness symptoms as an outcome (3,029 participants), this study found mask-wearing associated with a decreased risk of influenza-like-illness (overall risk ratio [RR] 0.83, 95% confidence interval [CI] 0.71 to 0.96). Studies examining laboratory-confirmed respiratory infections as an outcome (10,531 participants) showed no statistically significant association between mask-wearing and infections (RR 1.04, 95% CI 0.60 to 1.80). However, masking combined with enhanced hand hygiene was associated with a decreased risk for both influenza-like-illness symptoms (RR 0.88, 95% CI 0.51 to 1.51) and laboratory-confirmed respiratory infection (RR 0.79, 95% CI 0.52 to 1.18).

Conclusions:

Masking in community settings decreases transmission of influenza-like-illness. Mask-wearing combined with enhanced hand hygiene reduces transmission of influenza-likeillness and laboratory-confirmed respiratory infection.

Keywords: masking, community, transmission, respiratory, infection

INTRODUCTION

On March 11, 2020, the World Health Organization (WHO) classified “coronavirus disease 2019” (COVID-19) as a pandemic, as the levels of spread and severity of the disease increased rapidly worldwide.1 Non-pharmaceutical interventions are necessary to decrease the spread of the virus in community settings. These interventions include face mask-wearing, physical distancing, and hand hygiene.

Face mask use in healthcare facilities is widely accepted, with a number of studies now comparing the efficacy of various types of medical masks for the prevention of infection transmission.2–6 However, even amid the pandemic, with many states and municipalities mandating face mask use in enclosed community settings such as offices and schools, there has been no definitive answer on the efficacy of mask-wearing in community settings. In fact, opinions and policies vary greatly worldwide. Governments of various countries and the Centers for Disease Control and Prevention and WHO have disagreed on masking guidelines and changed views throughout the course of the pandemic.7–15

Under the threat of a relentless pandemic that could result in many more deaths across the globe, it is imperative that infection prevention and control interventions are based on current evidence. Therefore, this review aimed to generate data to support evidence-based public health policy development regarding mask-wearing in community settings. As there is little data examining the effectiveness of mask-wearing in the community for COVID-19, this rapid review examined the transmission of respiratory infections in general. It includes randomized controlled trials and summarizes the efficacy of mask-wearing on the transmission of respiratory infections in the community setting.

METHODS

Data Sources and Searches

This review followed the methods outlined in the McMaster Rapid Review Guidebook.16 The original search was conducted via PubMed from May 20–26, 2020. The search was then expanded in the following 2 weeks (end date, June 10, 2020) to include Google Scholar, Scopus, Health Evidence, and medRxiv (search terms in Appendix Table 1). The search was limited to English language articles. In addition, all relevant systematic reviews arising from the search were reviewed for additional primary literature matching the search criteria.2,17–29

Study Selection

Article titles were parsed for relevance in terms of study topic and setting. Relevant articles included studies focused on the efficacy of mask-wearing to reduce the spread of respiratory infections in community settings. Respiratory infections included in the analysis were any infection spread by aerosol or droplet, including but not limited to influenza A or B, rhinoviruses, coronaviruses, picornaviruses, enteroviruses, adenoviruses, respiratory syncytial virus human metapneumovirus and parainfluenza viruses.

Full texts of the articles deemed relevant were reviewed and reduced by study type. This rapid review focused solely on randomized controlled trials reporting quantitative data. Excluded were studies relating to respiratory virus transmission in healthcare settings and non-randomized controlled trials. Additional inclusion criteria included English language articles conducted with participants of any age in a community setting that measured influenza-like-illness (ILI) symptoms or laboratory-confirmed respiratory viruses as a study outcome. A comprehensive list of inclusion and exclusion criteria can be found in Appendix Table 2. The selected articles that met all inclusion criteria were confirmed by a second investigator and further examined for duplication; duplicate studies were removed.

Data Extraction and Quality Assessment

Two investigators extracted study data: title, author, year of study, year of publication, study design, methods, participants, number of participants, primary outcome, measurement of outcome, other outcomes, type of mask, comparator, results of control, results of interventions, whether the paper reported a significant difference according to their statistical standards, and papers’ self-identified strengths and limitations. After extraction by both investigators, data were compared to ensure accuracy and completeness. To establish consensus on the data extracted between the 2 investigators, any discrepancies were reviewed by the senior investigator.

Critical appraisal of each study was performed using the Cochrane Risk of Bias Tool30 via Covidence software (Melbourne, Australia). This assessment evaluated risk of bias in the following areas: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessors, incomplete outcome data, selective outcome reporting, and other potential sources of bias. The risk of bias for each aspect of the study was rated as high, low, or unclear by 2 investigators, and the individual assessment results were compared; any discrepancies were discussed until consensus was met. Following consensus evaluation, the reviewers gave each article an overall risk-of-bias rating. If an article had a high risk-of-bias rating in ≥2 categories, it was considered to have an overall high risk of bias. If an article had a high riskof-bias rating in 1 category and ≤2 unclear ratings, it was considered to have an overall medium risk of bias. Finally, if an article had no high risk-of-bias ratings and ≤2 unclear ratings, it was considered to have an overall low risk of bias (Appendix Tables 3 and 4).

Data Synthesis and Analysis

This analysis used the “META” package in STATA to construct forest plots for all the studies, examining masking data alone, enhanced hand hygiene alone and a combination of masking and enhanced hand hygiene, to compare against a control.31 Only quantitative data on rates of ILI and laboratory-confirmed respiratory infection from included publications were analyzed in forest plots. A fixed effects model was first used to calculate the individual and pooled risk ratios (RR). The level of heterogeneity was then calculated using the I2 statistic.32 Forest plots reporting substantial to considerable heterogeneity based on the following I2 index (low heterogeneity [I2 =0 – 40%], moderate heterogeneity [I2 =30 – 50%], substantial heterogeneity [I2 =50 – 90], and considerable heterogeneity [I2 = 75 – 100%], were re-calculated using the Dersimonian and Laird random effects model.33 Publication bias was assessed using contour-enhanced funnel plots and the Egger’s test. Two sided tests were used with all p-values ≤0.05 considered statistically significant. All analyses were conducted using STATA 16 (StataCorp LLC, College Station, TX).

RESULTS

Literature search

The database search yielded 37,366 titles. After removing duplicate articles and reviewing titles and abstracts, 56 full texts met initial inclusion criteria. Narrowing to randomized controlled trials left 11 eligible articles that were included in this rapid review (Figure 1).

Figure 1:

Figure 1:

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Literature search and selection.

Eleven studies were identified as randomized controlled trials of face mask use in the community, taking place between 2006 and 2015 (Table 1). In total, there were 9,140 participants across all intervention groups, and 6,918 participants across all control groups. Studies were conducted across the United States, Australia, China, Thailand, Germany, and France. Two studies were conducted in university residence halls, 2 during Hajj pilgrimages, and 7 in households. Nine studies collected data on self-reported ILI symptoms, and 10 studies used laboratory tests to confirm respiratory infection. Seven studies reported multiple interventions, including enhanced hand hygiene, education and masking or a combination. All studies used surgical masks for the masking intervention.

Table 1:

Randomized controlled trials measuring the effects of mask-wearing on the spread of respiratory viruses in community settings.

Author Setting Arms Primary Outcomes Type of Mask Control Group Adherence Intervention Group Adherence Overall Risk of Bias
Aiello A et al., 2010 39 US universities − Control (n=552)
− Mask (n=378)
− Mask and Hand Hygiene (n=367)
All groups were provided education on proper hand hygiene.		 Self-reported ILI symptoms and laboratory-confirmed influenza Tecnol procedure mask - Kimberly Clark Not reported Not reported Low
Aiello A et al., 2012 38 US universities − Control (n=370)
− Mask (n=392)
− Mask and Hand Hygiene (n=349) 		Self-reported ILI symptoms and laboratory-confirmed influenza Tecnol procedure mask - Kimberly Clark Used hand sanitizer 1.51 times per day − Mask and Hand Hygiene: wore face mask on average 5.08 hours per day, used hand sanitizer 4.49 times per day

− Mask: wore face mask on average 5.04 hours per day, used hand sanitizer 1.29 times per day		 Low
Alfelali M et al., 2019 35 Hajj pilgrimage with pilgrims from Australia, Saudi Arabia, and Qatar − Control (n=3823)
− Mask (n=3864) 		Laboratory-confirmed vRTIs and CRIs 3M standard tie-on surgical mask 14% reported wearing face mask daily, 35% reported wearing face mask intermittently − Mask: 25% reported wearing face mask daily, 48% reported wearing face mask intermittently Medium
Barasheed O et al., 2014 34 Hajj pilgrimage with Australian pilgrims − No Supervised Mask Group (n=53)
− Supervised Mask Group (n=36) 		Self-reported ILI symptoms and laboratory-confirmed respiratory infections 3M standard tie-on surgical mask 12% wore face masks − Supervised Mask Group: 76% wore face mask High
Canini L et al., 2010 48 Households with an infection in France − Control (n=158)
− Mask (n=148) 		Self-reported ILI symptoms AEROKYNH - LCH medical products for ages 10 and up; Face Mask KC47127 - Kimberly Clark for ages 5–10 Not reported − Mask: Used 2.5±1.3 masks per day, wore mask for 3.7±2.7 hours per day Low
Cowling B et al., 2009 40 Households with an infection in China − Control (n=279)
− Hand Hygiene (n=257)
− Hand Hygiene plus Mask (n=258)
All groups received education about the importance of healthy diet and lifestyle.		 Self-reported ILI symptoms and laboratory-confirmed influenza Surgical mask: Tecnol - The Lite One - Kimberly Clark 15% of index patients wore masks often, 7% of contacts wore masks often − Hand Hygiene: 85.7g of soap used, index patients used 2.7g of hand sanitizer, contacts used 1.4g of hand sanitizer, 31% of index patients wore masks often, 5% of contacts wore masks often

− Mask and Hand Hygiene: 78.9g of soap used, index patients used 1.6g of hand sanitizer, contacts used 1.4g of hand sanitizer, 49% of index patients wore masks often, 26% of contacts wore masks often		 Low
Larson E et al., 2010 36 Households with an infection in the US − Control (n=904)
− Hand Sanitizer (n=946)
− Hand Sanitizer and Face Mask (n=938)
All groups received materials regarding the prevention and treatment of URIs and influenza		 Self-reported ILI symptoms and URI and laboratory-confirmed influenza Procedure Face Masks for adults and children - Kimberly Clark 44.2% reported using hand sanitizer occasionally − Hand Hygiene: used a mean 12.1 ounces of hand sanitizer per month

− Mask and Hand Hygiene: used a mean 11.6 ounces of hand sanitizer per month, 50% of households with ILI reported using mask within 48 hours of episode onset		 Medium
MacIntyre C et al., 2009 50 Households with an infection in Australia − Control (n=100)
− Surgical Masks (n=94)
P2 Masks (n=92)
− Mask groups were always advised to wear their face masks when in the same room as the infected child.		 Self-reported ILI symptoms and laboratory-confirmed respiratory infections 3M surgical masks and 3M flat-fold P2 masks Not reported − Surgical Masks: 38% stated that they were wearing mask most or all the time on day 1, 31% on day 5

− P2 Masks: 46% stated that they were wearing mask most or all of the time on day 1, 25% on day 5

Overall 21% of participants in mask groups reported wearing mask often or always		 Low
MacIntyre C et al., 2016 49 Households with an infection in China − Control (n=295)
− Mask (n=302) 		CRI, ILI symptoms, and laboratory-confirmed respiratory infections 3M 1817 surgical mask Used mask for 1.4 hours per day − Mask: used mask for 4.4 hours per day Low
Simmerman J et al., 2011 41 Households with an infection in Thailand − Control (n=302)
− Hand Hygiene (n=292)
− Hand Hygiene plus Mask (n=291) 		Self-reported ILI symptoms and laboratory-confirmed influenza Standard paper surgical face masks (MedCon Company) 3.9 hand washes per day − HH: 4.7 hand washes per day

− Mask and HH: 4.9 hand washes per day, averaged 12 masks per person per week, averaged 211 minutes of mask-wearing per day		 Low
Suess T et al., 2012 42 Households with an infection in Germany − Control (n=82)
− Mask and Hand Hygiene (n=67)
− Mask Only (n=69) 		Clinical ILI and laboratory-confirmed influenza Child’s Face Mask - Kimberly Clark for children under 14, Aérokyn Masques - LCH Medical Products for adults Not reported − Mask: 12.9 face masks per person, 1.8 masks per day in 2010/2011

− Mask and HH: 12.6 masks per person, 1.7 masks per day in 2010/2011, 85.2mL of hand sanitizer in 2009/2010, 42.7mL of hand sanitizer in 2010/2011		 Low
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HH = hand hygiene; ILI = influenza-like-illness; vRTI = viral respiratory tract infection; CRI = clinical respiratory infection; URI = upper-respiratory infection. Risk of bias based on Cochrane Risk of Bias tool30

The overall risk of bias for the studies was generally low-to-medium. One study was identified, Barasheed et al.34, that rated high for potential risk of bias based on the criteria, due to small sample size and demographic differences between intervention groups. Alfelali et al.35 and Larson et al.36 both received an overall medium rank for risk of bias due to differences between intervention groups (Appendix Table 4).

Bias testing

On the contour enhanced funnel plot (Appendix Figure 1), the measure of the study effect size (log risk) against the variance (standard error) was relatively symmetrical showing no signs of publication bias. The Egger’s regression test of asymmetry was not statistically significant (p=0.54), also indicative that publication bias is absent.

Meta-analysis

Among the 7 studies evaluating mask-wearing alone that included ILI symptoms as an outcome, 14.5% (206/1419) of participants in the mask groups vs. 19.5% (314/1610) of those in the control groups showed ILI symptoms, and masking was associated with decreased risk of ILI symptoms (RR 0.83, 95% confidence interval [CI] 0.71to 0.96) (Figure 2). There was no heterogeneity (I2 0.00%, H2 1.00). Two of the 7 studies found results that favored the control group (weight 9.15, RR 1.02, 95% CI 0.61 to 1.71; weight 6.64, RR 1.26, 95% CI 0.69 to 2.31). In the other 5 studies, comprising 84.21% of the weight, masking was associated with reduced risk of ILI symptoms.

Figure 2:

Figure 2:

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Forest plot of estimations of the association between face mask use and influenza-like-illness symptoms.

ILI+ = showed influenza-like-illness symptoms; ILI- = did not show influenza-like-illness symptoms

Across the 7 studies evaluating mask-wearing alone that included laboratory-confirmed respiratory infection as an outcome, 3.51% (182/5188) of participants in mask groups vs. 3.22% (172/5343) of those in control groups had a laboratory-confirmed respiratory infection. There was no statistically significant association between masking and risk of infection (RR 1.04, 95% CI 0.60 to 1.80) (Figure 3). In contrast to ILI symptoms, these studies showed a noteworthy effect of heterogeneity (I2 56.14%, H2 2.28). Three of the 7 studies found masking associated with reduced risk of illness. The other 4 studies found masking was associated with increased risk of illness, comprising 58.98% of the total weight.

Figure 3:

Figure 3:

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Forest plot of estimations of the association between face mask use and laboratory-confirmed respiratory infection.

LC+ = laboratory-confirmed respiratory infection; LC- = no laboratory-confirmed respiratory infection

In the 5 studies that also examined the effects of hand hygiene, masking combined with elevated hand hygiene was associated with a lower risk of ILI symptoms (RR 0.88, 95% CI 0.51 to 1.51) (Appendix Figure 2). These 5 studies showed a larger effect of heterogeneity (I2 81.55%, H2 5.42). Only 1 of the studies showed results that favored the control group (weight 24.78, RR 2.04, 95% CI 1.31 to 3.17), while the other 4 studies associated masking and elevated hand hygiene with a reduced risk of ILI symptoms.

Lastly, in the 6 studies where it was examined, masking combined with improved hand hygiene was associated with a decreased risk of laboratory-confirmed respiratory infection (Appendix Figure 3). This was the strongest association among all the comparisons (RR 0.79, 95% CI 0.52 to 1.18). These 6 studies showed modest heterogeneity (I2 41.87%, H2 1.72). Only 1 of the studies showed results that favored the control group (weight 35.93, RR 1.18, 95% CI 0.86 to 1.62), and another study found no difference in infections between the groups (weight 4.67, RR 1.00, 95% CI 0.17 to 5.97). The other 4 studies, making up 59.40% of the total weight, favored masking and elevated hand hygiene as associated with a reduced risk of laboratory-confirmed respiratory infection.

DISCUSSION

This rapid review summarizes the evidence regarding the efficacy of face masks for reducing respiratory illness in the community setting – a critical question given the ongoing COVID-19 pandemic. The evidence derived from randomized controlled trials shows that masking in a community setting reduces self-reported ILI symptoms by 17%. However, it found limited evidence to support the same association between masking and transmission of laboratory-confirmed respiratory infections. On the other hand, masking combined with enhanced hand hygiene was associated with significantly reduced transmission both in terms of ILI (12% reduction) and laboratory-confirmed respiratory infection (21% reduction).

Surprisingly, the results of the analysis of the effect of face masks alone for reducing laboratory confirmed-respiratory were inconsistent with those for the analysis of reduction of ILI symptoms. One possible explanation for this could be bias and variation in self-reporting. ILI symptoms were measured by participant reports of qualifying conditions, such as cough, sore throat, chills, fever, headaches, body aches, etc., though exact definitions differed. Some studies used the CDC definition of ILI, which is a “fever (temperature of 100°F [37.8°C] or greater) and a cough and/or a sore throat without a known cause other than influenza,”37 while other studies simply required any listed symptoms to be noted by participants. Not only was reporting inconsistent across studies and participants, but certain symptoms could also have been due to allergies or other conditions beyond viral infection, ultimately skewing the ILI measurements. Multiple included papers addressed self-reporting issues in their limitations, stating specific problems with subjects underreporting symptoms36, reporting what they thought was expected20,38,39, and reporting ILI symptoms that were likely not due to influenza infection.39 Additionally, it is important to note that because only a subset of all upper respiratory infection-causing viruses were included in the analyses, ILI symptoms may also have resulted from viruses that were not included in laboratory analyses. For example, 3 of the 7 studies reporting laboratory confirmed infection rates in the face mask alone category tested only for influenza.

Furthermore, discrepancies also exist between the results of the analysis of face masks alone versus face masks in combination with enhanced hand hygiene, which may be due to viral transmissibility. In 5 out of the 6 studies included in the analysis of the effects of face masks with advanced hand hygiene38–42, influenza A and B were the only respiratory viruses tested for. According to a 2021 review by Leung evaluating the transmissibility of respiratory viruses43, infectious influenza viral particles have been recovered on surfaces suggesting possible roles for direct and indirect surface transmission of the influenza virus. Thus, hand hygiene may play a larger role in reducing transmission of influenza viruses – as was indicated in the studies analyzed here – than in other respiratory viruses that do not appear to use direct and/or indirect contact as a major mode of transmission, such as SARS-CoV-244. Future studies are needed to evaluate the roles of mask wearing versus hand hygiene in a wider range of respiratory viruses.

Overall, the findings were similar to other systematic reviews that have examined the benefit of masking in both healthcare and community settings2,17,18 with some important differences. Bin-Reza et al.18 found a limited evidence base to support the use of masks in healthcare or community settings but concluded that mask use is best undertaken as a package of personal protective measures, including good hand hygiene. The community randomized controlled trials included in the 2015 review by MacIntyre et al.2 suggested that face masks provide protection against respiratory infection in various community settings, though this protection is subject to adherence. Chu et al.17 also reported a lack of robust data but suggested that face masks were protective for people in the community who had been exposed to infection. Another rapid review relevant to COVID-19 found that data on the effectiveness of masking in community settings for preventing infections associated with coronaviruses were limited but suggest possible reduced risk for SARS1 transmission associated with masking45. Adding to this evidence, a cohort study conducted in Beijing, China during the pandemic produced results showing that face mask use by a COVID-19 positive patient prior to symptom development was 79% effective in reducing transmission in the household, while face mask use after the development of symptoms was not significantly effective46. In contrast to the prior systematic reviews, this review was limited to randomized controlled trials specific to community settings, providing us with the highest quality evidence from which to draw conclusions specific to the community setting.

A limitation of this analysis is that many studies reported adherence issues with mask-wearing or difficulty measuring and reporting adherence. Self-report was used as a measurement tool in 8 of 11 studies, and there was great variability in how adherence was measured amongst the studies, ranging from daily self-reported data to measurement of the amount of intervention material remaining at the conclusion of the study. As a result, it was difficult to set a uniform scale for adherence in order to assess its impact on measured outcomes. Lack of consistency related to adherence may influence individual study results, and thereby the results of this analysis. With many studies reporting low mask-wearing adherence among study participants, the inability to consider these data may have resulted in an underestimation of the effects of the interventions in this analysis and also may explain why this review did not find a reduction with masking and laboratory-confirmed respiratory infection. However, the prevalence of adherence issues among the studies may provide practical insight for public health officials when considering maskwearing mandates within a community setting. Looking at the greatest public health successes over the past few decades (e.g., tobacco control, seatbelt use, motor vehicle safety, childhood lead poisoning, fluoridation, immunization), few can be attributed to changing personal or individual behavior; instead, these successes are directly attributed to laws or mandates.47

When discussing limitations, it is also important to consider the additional limitations of the individual studies included in this rapid review. Foremost, there were different definitions of ILI within included studies, which made it difficult to make comparisons. In addition to varying definitions of ILI and the adherence issues discussed previously, several studies had small sample sizes and therefore were underpowered, limiting detection of small differences between intervention arms.34,36,39,42,48,49 Self-reported data, as discussed above, also present a potential source of bias. Moreover, in 2 studies, there was potential for infection in situations where masking was not required for the masking group – outside of the residence halls in Aiello et al.38 and at dinner time in MacIntyre et al.49 In the Cowling et al.40 study, there was potential bias due to the inclusion of symptomatic patients which may have resulted in higher viral shedding, unavoidable delay between symptom onset and application of intervention, and households with existing immunity. Lastly, in multiple studies there were widespread community hygiene efforts in place that may have influenced control group practices.35,36,41

CONCLUSIONS

In conclusion, this analysis found that masking in the community setting may be an effective way to slow the spread of respiratory illnesses. Future research should examine the impact of universal masking by the public on SARS-CoV-2 transmission. It should also address how best to maintain and measure adherence in a community or household setting as well as how to eliminate bias from reporting of ILI symptoms.

To reduce transmission of COVID-19, masking in community settings in combination with a sustained emphasis on adherence with hand hygiene best practices is recommended. The benefits of masking may be lost if hand hygiene is de-emphasized in community settings.

Acknowledgments:

MB was supported by a National Library of Medicine (NLM) training grant to the Computation and Informatics in Biology and Medicine Training Program (5T15LM007359). Research reported in this publication was also supported by the National Institute Of Allergy And Infectious Diseases of the National Institutes of Health (DP2AI144244). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Sources of Support:

MB was supported by a National Library of Medicine (NLM) training grant to the Computation and Informatics in Biology and Medicine Training Program (5T15LM007359). Research reported in this publication was also supported by the National Institute Of Allergy And Infectious Diseases of the National Institutes of Health (DP2AI144244). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Abbreviations:

COVID-19

Coronavirus Disease 2019

CI

Confidence interval

CRI

Clinical respiratory infection

HH

Hand hygiene

ILI

Influenza-like illness

RR

Risk ratio

URI

Upper-respiratory infection

vRTI

Viral respiratory tract infection

WHO

World Health Organization

APPENDIX

Appendix Figure 1:

Appendix Figure 1:

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Contour enhance funnel plot measuring study effect size (log risk) against variance (standard error).

Appendix Figure 2:

Appendix Figure 2:

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Forest plot of estimations of the association between face mask use combined with elevated hand hygiene and influenza-like illness symptoms.

ILI+ = showed influenza-like-illness symptoms; ILI- = did not show influenza-like-illness symptoms; HH = hand hygiene

Appendix Figure 3:

Appendix Figure 3:

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Forest plot of estimations of the association between face mask use combined with elevated hand hygiene and laboratory-confirmed respiratory infection.

LC+ = laboratory-confirmed respiratory infection; LC- = no laboratory-confirmed respiratory infection; HH = hand hygiene

Appendix Table 1:

Search strategies in various databases.

Database Search Terms
PubMed “public mask AND infection”, “mask AND infections”, “facemask AND MERS”, “facemask AND community”, “face mask AND community”, “community AND facemask AND infection”, “community AND face mask AND infection”, “((community settings) AND (infection prevention)) AND ((face masks OR face mask OR facemask OR mask))”
Google Scholar “((community settings) AND (infection prevention)) AND ((face masks OR face mask OR facemask OR mask))”
Scopus “((community settings) AND (infection prevention)) AND ((face masks OR face mask OR facemask OR mask))”, “community AND mask AND infection(s)”
Health Evidence “face mask AND community”, “facemask AND community”, “mask AND community”
medRxiv “face mask AND infection”, “facemask AND infection”, “((community settings) AND (infection prevention)) AND ((face masks OR face mask OR facemask OR mask))”
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Appendix Table 2:

Summary of criteria for article inclusion.

Inclusion Criteria Exclusion Criteria
Type of Study Cluster randomized trial Type of Study Cohort, cross sectional, case study, experimental, metaanalysis, systematic review, rapid review
Participants Humans Participants Animals/non-humans
Setting Community or public Setting Healthcare or laboratory
Language English Language Non-English
Abstract Available Abstract Not available
Outcome ILI symptoms or laboratory-confirmed respiratory virus Outcome No measure of ILI symptoms or laboratory-confirmed respiratory virus
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Appendix Table 3:

Description of biases addressed by the Cochrane Risk of Bias tool.

Bias Domain Issues Addressed
Sequence generation Was the allocation random? Would it result in comparable groups?
Allocation concealment Was the allocation sequence properly concealed? Could allocations have been foreseen?
Blinding of participants and personnel Were study participants blinded from the study intervention that they received?
Blinding of outcome assessors Were outcome assessors blinded from the study intervention participants received?
Incomplete outcome data Was the outcome data complete? Were there any exclusions? Were they properly reported?
Selective outcome reporting Was the possibility of selective outcome reporting addressed?
Other sources of bias Were limitations addressed? Was there a large enough sample size for generalizations? Were there confounding variables contributing to the results? Were intervention groups demographically comparable?
Overall risk of bias High means ≥ 2 high ratings; Medium means 1 high rating and ≤ 2 unclear ratings; Low means no high ratings and ≤ 2 unclear ratings
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Appendix Table 4:

Individual category and overall risk of bias scores for each study.

Author Sequence Generation Allocation Concealment Blinding of Participants and Personnel Blinding of Outcome Assessors Incomplete Outcome Data Selective Outcome Reporting Other Sources of Bias Overall Risk of Bias
Aiello A et al., 2010 (36) Low Low Low Unclear Low Unclear Low Low
Aiello A et al., 2012 (37) Low Unclear Low Low Low Low Low Low
Alfelali M et al., 2019 (38) Low Low Low Low Low Unclear High Medium
Barasheed O et al., 2014 (39) Unclear Unclear Low High Low Low High High
Canini L et al., 2010 (40) Low Low Low Low Low Low High Low
Cowling B et al., 2009 (41) Low Low Low Unclear Low Low Low Low
Larson E et al., 2010 (42) High Unclear Low Unclear Low Low Low Medium
MacIntyre C et al., 2009 (43) Unclear Unclear Low Low Low Low Low Low
MacIntyre C et al., 2016 (44) Low Low Low Low Unclear Low Low Low
Simmerman J et al., 2011 (45) Low Low Unclear Unclear Low Low Low Low
Suess T et al., 2012 (46) Low Low Low Unclear Low Low Low Low
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High = study showed clear red flags when addressing the bias issues in Appendix Table 3; Unclear = study did not address the bias issues in Appendix Table 3; Low = study properly addressed bias issues in Appendix Table 3

Footnotes

Conflict of Interest: None

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