Abstract

Objectives: to evaluate the effectiveness of non-woven face masks for the prevention of respiratory infections (MERS CoV, SARS-CoV, and SARS-CoV-2) in the population. Methods: search in Medline, Embase, Cinahl, The Cochrane Library, Trip databases. Google Scholar, Rayyan and medRxiv were also consulted for complementary results. No filters related to date, language or publication status were applied. Titles and abstracts were screened, and later, full texts were evaluated. Results: three studies were included: a randomized cluster clinical trial and two systematic reviews. The clinical trial indicates a potential benefit of medical masks to control the source of clinical respiratory disease infection. In one of the systematic reviews, it was not possible to establish a conclusive relationship between the use of the mask and protection against respiratory infection. Finally, another systematic review indicated that masks are effective in preventing the spread of respiratory viruses. Conclusion: Evidence points to the potential benefit of standard non-woven face masks. For the current pandemic scenario of COVID-19, education on the appropriate use of masks associated with individual protection measures is recommended.

Key words
Coronavirus of Middle East Respiratory Syndrome; Severe acute respiratory syndrome; Coronavirus; Masks; Prevention

Introduction

Since the first COVID-19 infection outbreak was acknowledged – registered in December 2019, at Wuhan, Mainland China –, there has been a great challenge on the use of Personal Protective Equipment (PPE) to prevent the spreading of the SARS-CoV-2 respiratory infection via droplets and aerosol during the COVID-19 pandemic¹1 Li Q, Guan X, Wu P, Wang X, Zhou L, Tong Y, Ren R, Leung KSM, Lau EHY, Wong JY, Xing X, Xiang N, Wu Y, Li C, Chen Q, Li D, Liu T, Zhao J, Liu M, Tu W, Chen C, Jin L, Yang R, Wang Q, Zhou S, Wang R, Liu H, Luo Y, Liu Y, Shao G, Li H, Tao Z, Yang Y, Deng Z, Liu B, Ma Z, Zhang Y, Shi G, Lam TTY, Wu JT, Gao GF, Cowling BJ, Yang B, Leung GM, Feng Z. Early Transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia. N Engl J Med 2020; 382(13):1199-1207.^,22 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733..

According to the International Sanitary Regulation (IRS), to assure maximum safety against the transmission of this disease, due to the high morbidity and mortality rates caused by SARS-CoV-2, measures were adopted to reduce its effects and negative impacts on the population. In order to broaden priority actions, Brazil started to create technical norms for the use of personal protective equipment against the current pandemic, including the guidelines for the use of surgical and protective masks³3 Organização Mundial da Saúde (OMS). WHA58.3, Revision of the International Health Regulations. Genebra: OMS; 2005..

During this time, studies focused on which type of mask should be made available to prevent the spreading of the pandemic. The so-called surgical masks protect against infectious agents transmitted by droplets. They are disposable, made for personal use, and filters bacteria up to 98%, as recommended by the NE-14683 European Standard. These surgical masks must have three independent layers of “spunbond-meltblown-spunbond” (non-woven fabric used for dental, medical and hospital operations), in compliance with the Brazilian norm ABNTNBR 15052⁴4 Agência Nacional de Vigilância Sanitária (Anvisa). Nota técnica GVIMS/GGTES/ANVISA, nº 04/2020. Orientações para serviços de saúde: medidas de prevenção e controle que devem ser adotadas durante a assistência aos casos suspeitos ou confirmados de infecção pelo novo coronavírus (sars-cov-2) (atualizada em 31/03/2020). Brasília: Anvisa; 2020..

The other type of mask, categorized as “protective mask”, is known as N95 or FFP 2 (filtering facepiece), or equivalent, personal respirator and follows the EN-149: 2991 European Standard. This respirator broadens the specter for filtering aerosol and, depending on the standards and laws of each country, can be reused. It protects against infectious agents transmitted through droplets, and prevents inhaling airborne infectious agents (aerosol) and droplets the same size or smaller than 5μm⁴4 Agência Nacional de Vigilância Sanitária (Anvisa). Nota técnica GVIMS/GGTES/ANVISA, nº 04/2020. Orientações para serviços de saúde: medidas de prevenção e controle que devem ser adotadas durante a assistência aos casos suspeitos ou confirmados de infecção pelo novo coronavírus (sars-cov-2) (atualizada em 31/03/2020). Brasília: Anvisa; 2020.^,55 Agência Nacional de Vigilância Sanitária (Anvisa). Resolução de Diretoria Colegiada - RDC Nº 356, de 23 de março de 2020. Dispõe, de forma extraordinária e temporária, sobre os requisitos para a fabricação, importação e aquisição de dispositivos médicos identificados como prioritários para uso em serviços de saúde, em virtude da emergência de saúde pública internacional relacionada ao SARS-CoV-2. Diário Oficial da União 2020; 23 mar..

Due to a global lack of supplies, the World Health Organization now recommends the use of masks for the general population. However, what are the available evidences of non-woven masks in preventing respiratory diseases caused by coronaviruses (MERS CoV, SARS-CoV and SARS-CoV-2) to the general population? This question takes into account the comparison of non-woven mask use with other face masks or non-face mask use at all.

Masks for non-health workers are the ones made with two-layer fabric and with “spunbond”, a type of non-woven that cannot filter agents inside dental, medical and hospital facilities. They are not recommended for healthcare professionals and should be restricted for non-professionals, to protect them against respiratory diseases like COVID-19⁶6 World Health Organization (WHO). Advice on the use of masks in the context of COVID-19: interim guidance, 6 April 2020. Geneva: WHO; 2020. [Contract No.: WHO/2019-nCov/IPC_Masks/2020.3].

Thus, the objective of this systematic review is to evaluate and gather the available scientific evidence regarding face masks efficacy for the prevention of respiratory diseases caused by MERS CoV, SARS-CoV e SARS-CoV-2 to the general population.

Methods

Inclusion criteria

Studies as systematic reviews, meta-analysis, clinical trials, randomized or not (humans) or observational – which evaluated the use of non-woven face masks or the non-use of masks by the general population to prevent viral respiratory diseases (MERS-CoV, SARS-CoV e SARS-CoV-2) were considered for inclusion in the present review. Filters related to date, language or publishing status were not applied (Chart 1).

Exclusion criteria

Studies evaluating healthcare professionals, surgical masks, N95 or FFP respirators, as well as pre-clinical studies, or laboratory studies, assessment of health technology, editorials, commentary or opinion studies, and narrative reviews were excluded (Chart 2).

Information sources and search strategies

The search was conducted on the following databases: Medline/Pubmed, Embase, Cinahl, The Cochrane Library and Trip Database. Search strategies used a combination of subject headings and free text terms to address the following subjects “Coronavirus”, “Covid-19”, “Acute Respiratory Distress Syndrome” and “Masks”. Google Scholar, Rayyan, medRxiv were used as a complementary search. The searches were conducted on April 2nd, 2020 and were last updated on April 8, 2020 (Chart 3).

Results

Selecting studies

After databases and complementary searches, 1,132 studies were identified; after duplicate exclusion, 679 articles were screened by title and abstract. The remaining 69 articles were read in full and 17 were selected for data extraction. However, in the end, only 3 studies fulfilled inclusion/exclusion criteria: 1 randomized cluster clinical trial⁷7 MacIntyre CR, Zhang Y, Chughtai AA, Seale H, Zhang D, Chu Y, Zhang H, RahmanB, Wang Q. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness. BMJ Open 2016; 6(12):e012330. and 2 systematic reviews⁸8 Benkouiten S, Brouqui P, Gautret P. Non-pharmaceutical interventions for the prevention of respiratory tract infections during Hajj pilgrimage. Travel Med Infect Dis 2014; 12(5):429-442.^,99 Liang M, Gao L, Cheng C, Zhou Q, Uy JP, Heiner K, Sun C. Efficacy of face mask in preventing respiratory virus transmission: a systematic review and meta-analysis. RedRxiv 2020; [acessado 2020 Maio 06]. Disponível em: https://doi.org/10.1101/2020.04.03.20051649
https://doi.org/10.1101/2020.04.03.20051... .

Randomized clinical trial

MacIntyre et al.⁷7 MacIntyre CR, Zhang Y, Chughtai AA, Seale H, Zhang D, Chu Y, Zhang H, RahmanB, Wang Q. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness. BMJ Open 2016; 6(12):e012330. is a randomized cluster clinical trial about the risk of infection by respiratory diseases similar to influenza among people who live with an infected person. The intervention was the comparison of mask use with non-mask use. No statistically significant results comparing the use of masks and risk of infection were found. However, there were relevant results for mask use and risk reduction to develop influenza-like respiratory diseases.

In the intention-to-treat analysis, the relative risk (RR) for clinical respiratory disease was [0.61, 95% CI 0.18 - 2.13], ILI RR [0.32, 95% CI 0.03 - 3.13], and for laboratory-confirmed viral infections was RR [0.97, 95% CI0.06 - 15.54], which were consistently lower in the mask group in comparison with the no mask group, although not statistically significant. The viruses were isolated in 60% (146/245) of the index cases. Influenza was the most common virus isolated from 115 participants (47%): influenza A, 100; influenza B, 1, and influenza A and B, 4. Other isolated viruses from the index cases were rhinovirus, NL63 and C229E. More than one virus was isolated in 48 (20%) index cases, including 17 influenza co-infections.

The study’s risk of bias assessment using the ROB 2.0¹⁰10 Sterne JAC, Savovic J, Page MJ, Elbers RG, Blencowe NS, Boutron I, Cates CJ, Cheng HY, Corbett MS, Eldridge SM, Emberson JR, Hernán MA, Hopewell S, Hróbjartsson A, Junqueira DR, Jüni P, Kirkham JJ, Lasserson T, Li T, McAleenan A, Reeves BC, Shepperd S, Shrier I, Stewart LA, Tilling K, White IR, Whiting PF, Higgins JPT. RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ 2019; 366:l4898. tool was evaluated as unclear. Even though the research presents methodological rigor, the study does not provide clear information on the randomization method of the evaluated participants. Moreover, in addition to the use of masks, the intervention group received information on frequent hand washing. This may have contributed to the observed difference, even if not statistically significant. The study points to a potential benefit with medical masks for the disease control, however, it is limited by low sample size and low secondary attack rates (SAR)⁷7 MacIntyre CR, Zhang Y, Chughtai AA, Seale H, Zhang D, Chu Y, Zhang H, RahmanB, Wang Q. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness. BMJ Open 2016; 6(12):e012330..

Systematic reviews

The review carried out by Benkouiten et al.⁸8 Benkouiten S, Brouqui P, Gautret P. Non-pharmaceutical interventions for the prevention of respiratory tract infections during Hajj pilgrimage. Travel Med Infect Dis 2014; 12(5):429-442. assessed the use of nonpharmaceutical interventions (NPIs) for respiratory tract infections (RTI) prevention during the pilgrimage to Hajj, Mecca. The review included 17 studies which conducted descriptive analysis of the results. Several prevention measures against respiratory tract infections were analyzed, including face mask use. The results on mask effectiveness for respiratory tract infections prevention were conflicting. According to the applied tool for critical appraisal (AMSTAR 2)¹¹11 Shea BJ, Reeves BC, Wells G, Thuku M, Hamel C, Moran J, Moher D, Tugwell P, Welch V, Kristjansson E, Henry DA. AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both. BMJ 2017; 358:j4008., the review presented a low methodological quality.

Face masks effectiveness to prevent respiratory disease transmission similar to influenza and RTIs relies on many aspects, such as its strict and correct use and hand washing. Although most studies included in the aforementioned review have pointed out that mask use was associated with a reduced risk of severe acute respiratory syndrome, none of them presented a conclusive relation between mask use and protection against respiratory diseases similar to influenza. Nonetheless, Benkouiten et al.⁸8 Benkouiten S, Brouqui P, Gautret P. Non-pharmaceutical interventions for the prevention of respiratory tract infections during Hajj pilgrimage. Travel Med Infect Dis 2014; 12(5):429-442. recommend that face masks should be consistently and correctly used from the very beginning of pilgrimage, even though the available studies do not provide strong evidence of its effectiveness in preventing viral respiratory infections.

The systematic review conducted by Liang et al.⁹9 Liang M, Gao L, Cheng C, Zhou Q, Uy JP, Heiner K, Sun C. Efficacy of face mask in preventing respiratory virus transmission: a systematic review and meta-analysis. RedRxiv 2020; [acessado 2020 Maio 06]. Disponível em: https://doi.org/10.1101/2020.04.03.20051649
https://doi.org/10.1101/2020.04.03.20051... assessed mask use and the association with infection by respiratory coronavirus of the severe acute respiratory syndrome (SARS-CoV), influenza, H1N1 and SARS-CoV-2. The 21 included studies that reported the use of mask effectiveness observed 8,686 subjects. In general, masks are effective in preventing the spread of respiratory viruses: after the use of mask, the risk of viral respiratory infection was significantly reduced in 35% [OR = 0.35.95% CI = 0.24-0.51, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 60%]. In the healthcare workers subgroup, the protective effect was more significant, with risks of infection reduced by 20% [OR = 0.20. 95% CI = 0.11-0.37, I² = 59%]. In a study on COVID-19, the risk of infection reduced by 4% [OR = 0.04. 95% CI = 0.00-0.60]. In the non-healthcare workers subgroup, there was a protective effect, with risks of infection 53% lower [cluster OR = 0.53. 95% CI = 0.36 - 0.79, I² = 45%]. A more thorough description found significant effects in the household subgroup, with 60% lower risk of respiratory viral infections[OR = 0.60. 95% CI= 0.37-0.97, I² = 31%] and non-household subgroup, with 44% lower risk [OR = 0.44, 95% CI= 0.33-0.59, I² = 54%]. One study included healthcare workers and patients’ family members, with 74% lower risk of infection by respiratory viral diseases [OR = 0.74. 95% CI: 0.29-1,90].

By geographic locations, beneficial effects of the mask use were found in Asia (31% lower risk) [OR = 0.31, 95% CI = 0.19-0.50, I² = 65%] and in Western countries (45% lower risk) [OR = 0.45, 95% CI = 0.24-0.83, I² = 51%]. Healthcare workers in Asia (21% lower risk) [OR = 0.21, 95% CI = 0.11-0.41, I² = 64%] and in Western countries (11% lower risk) [OR = 0.11, 95% CI = 0.02-0.51, I² = 0%] may have significantly reduced the risks by using masks. In the non-healthcare workers subgroup, a protective effect was observed in Western countries (46% lower risk) [OR = 0.46, 95% CI = 0.34-0.63, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 57%] and in Asia (51% lower risk) [OR = 0.51, 95% CI = 0.34-0.78, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 45%]. Masks showed protective effect against influenza virus (55% lower risk) [OR = 0.55, 95% CI = 0.39-0.76, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 27%], SARS (26% lower risk) [OR = 0.26, 95% CI = 0.18-0.37, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 47%] and SARS-CoV-2 (4% lower) [OR = 0.04, 95% CI = 0.00-0.60, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 0%]. However, no significant protective effect against H1N1 was observed [OR = 0.30, 95% CI = 0.08-1.16, I²2 Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R, Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W, China Novel Coronavirus Investigating and Research Team. A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 2020; 382(8):727-733. = 51%] (9). The critical appraisal carried out through AMSTAR 2 (11) indicates the high quality of this systematic review.

Discussion

Evidence synthesis

The results regarding masks effectiveness were conflicting. This initially happened due to the lack of definition of mask types used in the studies: most refer to them only as ‘masks’ or ‘face masks’. Nonetheless, there was a significant result for non-woven face mask use linked to the risk reduction of influenza-like respiratory illness. The use of non-woven face masks has been identified as an important barrier against droplet and aerosol dispersion related to COVID-19, even without filtration capacity for dental, medical and hospital environments⁴4 Agência Nacional de Vigilância Sanitária (Anvisa). Nota técnica GVIMS/GGTES/ANVISA, nº 04/2020. Orientações para serviços de saúde: medidas de prevenção e controle que devem ser adotadas durante a assistência aos casos suspeitos ou confirmados de infecção pelo novo coronavírus (sars-cov-2) (atualizada em 31/03/2020). Brasília: Anvisa; 2020..

Another key element is that the mask use does not reduce or substitute the need for the prescribed hygiene measures, especially hand washing, and more than 1-meter (3.3 feet) distance from one another in public spaces. Moreover, non-woven masks must be affordable for the general population. Other aspects should also be assessed, such as the type of material and 20 to 40 g/m² grammage, as recommended by ANVISA (Brazilian Health Regulatory Agency). The manufactured product must be in 3 layers: a layer of non-waterproof fabric on the front, breathable fabric in the middle and a cotton fabric on the part in contact with the face surface⁵5 Agência Nacional de Vigilância Sanitária (Anvisa). Resolução de Diretoria Colegiada - RDC Nº 356, de 23 de março de 2020. Dispõe, de forma extraordinária e temporária, sobre os requisitos para a fabricação, importação e aquisição de dispositivos médicos identificados como prioritários para uso em serviços de saúde, em virtude da emergência de saúde pública internacional relacionada ao SARS-CoV-2. Diário Oficial da União 2020; 23 mar..

Conclusion

The evidence found in this systematic review points to a potential benefit in the use of non-woven mask by the general population to prevent the COVID-19. However, there are limitations due to the small number of articles available and the low-quality methods of two of the studies assessed, which presented several biases that jeopardize them. In this COVID-19 pandemic scenario, the population should be provided with the following instructions: the current World Health Organization (WHO) recommendations or local guidelines; education on the proper use of masks; education on the adequate use of non-woven masks and/or other types of masks as an auxiliary method, associated with hand washing and other individual protection measures. However, further investigations on the effectiveness of non-woven masks compared to other types of masks for the general population are important, in order to provide guidelines on protection measures against the COVID-19 epidemic.

Strengths and limitations of the systematic review

This systematic review presents methodological precautions, such as important databases research and methodological quality assessment of the included studies used for this paper. Nevertheless, there were some restricting aspects, such as the low number of articles and low methodological quality of two of them. Even though the evidence considered for this systematic review points to potential benefits of non-woven mask use for COVID-19 prevention by the general population, it is not possible to establish a conclusive result, since there are only few primary studies addressing non-woven face masks, and or other types of masks, compared to non-mask use to prevent SARS-CoV-2 in the general population.

References

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History