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A revised tool for assessing risk of bias in randomized trials. Low risk of bias was considered when all key domains were considered at low risk; unclear risk of bias was considered when one or more key domains were unclear and high risk of bias was considered when one or more key domains were considered at high risk.

A meta-analysis was not feasible due to the high methodological heterogeneity identified; however, a detailed qualitative synthesis of the evidence of the included studies was performed using GRADE Grading of Recommendations Assessment, Development and Evaluation.

GRADE guidelines: 3. Rating the quality of evidence. J Clin Epidemiol. After the removal of duplicates through the Endnote manager, titles and abstracts were examined. From those 15 studies, six were excluded: one did not define the type of compared masks; 16 Effectiveness of disposable face masks in preventing cross contamination during dental procedures.

J Dent Res. Practices around the use of masks and respirators among hospital health care workers in 3 diverse populations. Am J Infect Control. Availability, consistency and evidence-base of policies and guidelines on the use of mask and respirator to protect hospital health care workers: a global analysis.

BMC Res Notes. Ann Occup Hyg. Kim SW. Optical microscopic study of surface morphology and filtering efficiency of face masks. Peer J. Table 1. One additional article was identified after hand search and another was found through a search alert. Finally, 11 articles were selected and included in the qualitative synthesis of this systematic review. Testing the efficacy of homemade masks: would they protect in an influenza pandemic?

Disaster Med Public Health Prep. Furuhashi M. A study on the microbial filtration efficiency of surgical face masks—with special reference to the non-woven fabric mask. Bull Tokyo Med Dent Univ. Simple respiratory protection: evaluation of the filtration performance of cloth masks and common fabric materials against nm size particles. Effectiveness of face masks used to protect Beijing residents against particulate air pollution. Occup Environ Med. Understanding the factors involved in determining the bioburdens of surgical masks.

Ann Transl Med. Professional and home-made face masks reduce exposure to respiratory infections among the general population. PLoS One. Comparison of filtration efficiency and pressure drop in anti-yellow sandmasks, quarantine masks, medical masks, general masks, and handkerchiefs. Aerosol Air Qual Res. Ann Intern Med. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano. The summaries of qualitative and quantitative data are shown in Table 2 and Table 3 respectively.

Attempts to communicate by email with corresponding authors were made when data were unavailable. However, only one author responded. According to each type of study, a different tool for assessing RoB was used. From the 11 selected studies for qualitative analysis, there were nine laboratory studies, one non-randomized clinical trial and one randomized clinical trial complemented by laboratory data.

RoB was performed separately for each outcome within each study. An adapted JBI checklist for Quasi-Experimental Studies experimental studies without random allocation was applied to ten studies. Evaluating the efficacy of cloth facemasks in reducing particulate matter exposure. J Expo Sci Environ Epidemiol. Seven domains were evaluated: randomization processes; clearly described methods, interventions, outcome measures; blinding of the assessments; reliable measurement of outcomes and proper statistical analysis Table 4.

Only three studies 13 Five studies 13 Four studies 22 Only one study presented a high RoB 24 The major reason for this RoB rating was due to bias in selection of participants, who had been invited to participate in the research; and bias in classifying interventions since it did not report if the cough velocity was measured and if the patients were under treatment, which can be confounders since the cough velocity and the use of medications can modify the results.

In addition, no inclusion and exclusion criteria of participants had been established and this can lead to a heterogeneous sample and unrealistic results. For the cluster randomized trial, 13 RoB was evaluated according to the Cochrane collaboration RoB 2.

Regarding the material used in the face masks, six studies evaluated several household materials that could possibly be used for making cloth masks, 23 Four studies compared cloth masks with surgical masks only, 23 Table 2. Regarding the experimental model, performed by simulation, five studies used NaCl aerosol with particles size reported: 0. One study 22 Three studies evaluated more than one outcome, and also used volunteers. One study 30 The first one 23 Cotton mix The second one 24 Three studies 13 The first one 22 The last one 31 The first one 25 The remaining two 26 One 25 The other 26 Occupational health was evaluated by only one study 13 Protection factor 28 The protection factor of cloth, surgical and FFP-2 masks were evaluated by one study 28 Protection offered by a surgical mask and FFP2 respirator did not differ.

Two studies 23 Studies evaluating pressure drop PD 23 However, they can cause a suffocating sensation to the user. On the other hand, some of the evaluated fabrics presented a good breathability, such as calico, 24 One study 31 GRADE assessment was divided into anti-contamination and anti-transmission and breathability outcomes. For the outcomes included in the anti-contamination the quality of the evidence ranged from low to moderate level Occupational health.

For the anti-transmission and breathability outcomes, the quality of the evidence ranged from very low to moderate due to the bias of the included studies and magnitude of effect Tables 7 and 8. Regardless of some benefits for cloth mask users, the results are hard to summarize and generalize because of the variety of fabrics and layers evaluated.

These results should be viewed with caution given the quality of the evidence and the fact that almost all the included studies evaluated the outcome of interest in a laboratory setting. Furthermore, elements of statistical precision between the groups are scarce, and outcomes such as degree of protection, pressure drop, surface masks test and occupational health were each evaluated in only one study.

Our results suggest that cloth masks present worse outcomes for filtration efficiency, penetration level and protection factor in comparison with medical masks, when evaluated in a laboratory-based examining small particles.

In accordance with other study 8 8. Size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities. J Aerosol Sci. Duguid JP. The size and the duration of air-carriage of respiratory droplets and droplet-nuclei. J Hyg Lond. For this reason, it is suggested that the use of cloth masks by the general public is likely a useful public health measure in reducing COVID contamination and transmission.

In addition, the fact that cloth masks are not as effective as surgical masks does not mean that they provide no protection. Anything that contributes to controlling the spread of a virus should be encouraged from a population-based point of view. Multiple approaches that alone do not a have a major impact when combined could have a multiplicative effect in slowing the spread of a virus like COVID by reducing the transmission rate.

See Table 3. Overall, the filtration efficiency of the fabric depends on a variety of factors: the composition of the fabric and some characteristics of the particles to which it is exposed such as their size and velocity. These factors are fundamental to evaluate the quality of the masks. Only seven studies 22 J Med Virol. This lack of complete information directly affected the potential bias of these studies. If the particle sizes were known, we could have better evaluated the efficiency of cloth masks for the general population against the coronavirus.

Only one study 30 The other studies assessed other types of bacteria and viruses, but this did not seem to affect the results. The study that evaluated the use of cloth masks by healthcare workers 13 A recent systematic review 35 Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff.

The authors highlighted the urgent need for randomized clinical trials with better methodological quality. However, results in a healthcare setting are not readily generalizable to the population where any measure, even not as efficient as a measure in a healthcare setting, can provide some source control.

Another recent systematic review 36 Regarding the use of face masks, it was found that it could result in a large reduction in risk of infection, with stronger association with N95 or similar respirators when compared with surgical masks. Are you and others around you fully vaccinated? Are you immunocompromised? The riskier the situation, the more likely the higher-quality mask is the best option. Not only is layering important to improve filtration but so is fit.

A CDC-recommended technique for improving the fit of either a cloth or surgical mask is knotting the straps and tucking the sides.

A mask is generally a good fit if you feel warm air coming through the front of the mask as you inhale and exhale. A large-scale, real-world study published this month found surgical masks especially effective at reducing symptomatic infections.

These types of masks prevented 1 in 3 infections among people 60 and older. Researchers from Yale, Stanford, and the nonprofit GreenVoice monitored more than , adults in rural Bangladesh for at least eight weeks. Roughly half the Bangladeshis received interventions like free mask distribution and promotion.

The same villages reported fewer confirmed Covid infections and a lower incidence of related symptoms. Villages where cloth masks were given out reported an 8. This study was conducted before the delta variant was circulating widely in the country.

The study has not yet undergone peer review, but some experts have already heralded its methodology and results. They are probably better than nothing. Abaluck suspects his study offers mixed evidence for cloth masks because only about a third of those who reported symptoms consented to blood testing for Covid.

In other words, the sample size was too small to observe anything significant. They actually do make you less likely to get Covid. At this point, cloth masks are so ubiquitous in the United States that it can be easy to forget that they were originally supposed to be a stopgap measure. In April , when surgical masks and highly coveted N95s were first in short supply, the CDC released its initial mask guidance and said cloth masks were the way to go for most people —noting that they could be sewn at home from old T-shirts.

We might have once hoped that vaccines would entirely obviate masking, but unfortunately, masks seem poised to stick around for quite some time. And yet, even as much of our approach to the pandemic has changed in the past 18 months, our approach to masking largely has not.

So why are we still strapping pieces of fabric to our face? Read: The masks were working all along. Unless you work in health care, the CDC still recommends masks made with at least two layers of washable, breathable fabric.

A big reason for this is that, yes, surgical masks are still in limited supply , according to the FDA, and so they must be prioritized for health-care workers. Though the shortage appeared to relent this summer, when widespread vaccination led to a dip in demand for both surgical and cloth masks , the rise of the Delta variant precipitated another major mask crunch.

Part of the problem is that the enduring mask wars have helped frame mask wearing as a simple binary.