70+ Studies Proving Masks Work

In today’s Medium article, I’ll be posting 70 studies+ proving that masks work and are effective in preventing the transmission of viral infections. These studies will range from RCTs to case studies and meta-analyses. So without further ado, let’s get into the article.

1. Face masks considerably reduce COVID-19 cases in Germany: https://www.pnas.org/content/early/2020/12/02/2015954117
2. A recent study out of the UK, for example, showed that mandates to wear masks could be enough to contain an outbreak without a lockdown: https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2020.0376
3. “Masks serve a dual purpose to protect the wearer and others.” — https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2774266
4. We produced the mask and carried out subjective testing on a user in a typical workplace setting; we demonstrated that the mask was form-fitting, customizable, washable, and could be worn continuously and routinely over extended periods of time by individuals and therefore could serve as an effective means to reduce the harm from SARS-CoV-2: https://www.tandfonline.com/doi/abs/10.1080/00405000.2020.1805971
5. The potential of face masks to reduce the spread of respiratory infections could be useful. Wang et al1 indicated that 10 of 213 medical professionals with no mask were infected by COVID-19 as compared with 0 of 278 wearing N95 respirators: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173698/
6. In the meanwhile, reducing dispersion through simple measures, such as surgical masks and careful fitting of the interfaces and sealing of the circuit on supported patients are strongly recommended: https://link.springer.com/article/10.1007/s00134-020-06314-w
7. One recent study in BMJ Global Health looked at transmission of SARS-CoV-2 in 124 families in which at least one member had COVID-19. The data showed that face masks were “79% effective in reducing transmission” if the person with COVID-19 wore them before they developed symptoms.
   https://gh.bmj.com/content/5/5/e002794.abstract
8. Low-cost measurement of face mask efficacy for filtering expelled droplets during speech (FULL): https://advances.sciencemag.org/content/advances/suppl/2020/08/07/sciadv.abd3083.DC1/abd3083_SM.pdf
9. Research papers have shown that simple face coverings can reduce the number of droplets, and perhaps some aerosols, to some extent.
   https://onlinelibrary.wiley.com/doi/10.1111/jep.13415
10. An experiment using high-speed video found that hundreds of droplets ranging from 20 to 500 micrometres were generated when saying a simple phrase, but that nearly all these droplets were blocked when the mouth was covered by a damp washcloth.
    https://www.nejm.org/doi/full/10.1056/NEJMc2007800
11. “In our investigation, the transmission may have been mitigated by mild symptoms and masking during the flight” https://www.cmaj.ca/content/192/15/E410
12. Looked at coronavirus deaths across 198 countries and found that those with cultural norms or government policies favouring mask-wearing had lower death rates. https://www.researchgate.net/publication/342198360_Association_of_country-wide_coronavirus_mortality_with_demographics_testing_lockdowns_and_public_wearing_of_masks_Update_June_15_2020
13. People who had influenza or the common cold found that wearing a surgical mask significantly reduced the amount of these respiratory viruses emitted in droplets and aerosols
    https://www.nature.com/articles/s41591-020-0843-2#Sec3
14. The potential of face masks to reduce the spread of respiratory infections could be useful. Wang et al1 indicated that 10 of 213 medical professionals with no mask were infected by COVID-19 as compared with 0 of 278 wearing N95 respirators: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173698/
15. Viral particles were not found in the Petri dishes after coughing while wearing the N95 mask or the KF94 mask: https://www.tandfonline.com/doi/abs/10.1080/23744235.2020.1810858
16. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818
17. (First Randomized, Controlled Clinical Trial of Mask Use in Households)
    “In an adjusted analysis of compliant subjects, masks as a group had protective efficacy in excess of 80% against clinical influenza-like illness” — https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext
18. META-ANALYSIS: “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-Person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-Analysis” https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext
19. Cloth face coverings, even homemade masks made of the correct material, are effective in reducing the spread of COVID-19 — for the wearer and those around them: https://royalsociety.org/-/media/policy/projects/set-c/set-c-facemasks.pdf?la=en-GB&hash=A22A87CB28F7D6AD9BD93BBCBFC2BB24
20. The introduction of a mandatory mask policy was associated with an estimated 23% reduction in the effective reproduction ratio, from 1.18 to 0.91. The mandatory mask use policy substantially increased public use of masks and was associated with a significant decline in COVID-19 transmission after the introduction of the policy: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3714648
21. “Face mask use could result in a large reduction in risk of infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD -14·3%, -15·9 to -10·7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable 12–16-layer cotton masks; pinteraction=0·090; posterior probability >95%, low certainty).”: https://pubmed.ncbi.nlm.nih.gov/32497510/
22. Exposing society to SARS-CoV-2 without the unacceptable consequences of severe illness with public masking could lead to greater community-level immunity and slower spread as we await a vaccine. https://pubmed.ncbi.nlm.nih.gov/32737790/
23. “In conclusion, our findings suggest that face mask use should be as nearly universal (i.e., nation-wide) as possible and implemented without delay, even if most masks are homemade and of relatively low quality.” https://www.sciencedirect.com/science/article/pii/S2468042720300117
24. “Mask wearing by all individuals, supported by proper education and training of mask making and appropriate usage, can be an effective strategy in conjunction with social distancing, testing and contact tracing, and other interventions to reduce disease transmission.” https://www.sciencedirect.com/science/article/pii/S2352431620301802#sec2
25. We show that during indoor coughing some saliva particulates could travel up to 0.48 m, 0.73 m, and 2.62 m for the cases with medical-grade, non-medical grade, and without facial masks, respectively. Thus, in indoor environments either medical or non-medical grade facial masks can successfully limit the spreading of saliva particulates to others: https://arxiv.org/abs/2011.03394
26. Based on the literature reviewed, it is safe to say that wearing face masks at the community level and in medical settings will decrease the spread of COVID-19 by: 1. Preventing Sars-CoV-2 droplets from leaving the infected wearer and entering the environment. 2. Preventing Sars-CoV-2 droplets from entering the respiratory tract of the uninfected wearer: https://rgust.edu.gy/wp-content/uploads/2020/10/The-Effectiveness-of-Different-types-of-Face-Masks.pdf
27. However, the use of MNC seems to be linked to relevant protection during close contact scenarios by limiting pathogen-containing aerosol and liquid droplet dissemination. (for context MNC = mouth and nose covering): https://pubmed.ncbi.nlm.nih.gov/32787926/
28. Multilayer cloth masks, designed to fit around the face and made of water-resistant fabric with a high number of threads and finer weave, may provide reasonable protection: https://pubmed.ncbi.nlm.nih.gov/32639930/
29. Community-wide mask wearing may contribute to the control of COVID-19 by reducing the amount of emission of infected saliva and respiratory droplets from individuals with subclinical or mild COVID-19: https://www.sciencedirect.com/science/article/abs/pii/S0163445320302358
30. Our findings provided valuable details of pre-symptomatic patient mask-wearing and restriction of mass gathering in congested spaces particularly, are important interventions to mitigate the SARS-CoV-2 transmission: https://www.sciencedirect.com/science/article/pii/S1477893920302994
31. Viral particles were not found in the petri dishes after coughing while wearing the N95 mask or the KF94 mask: https://www.tandfonline.com/doi/abs/10.1080/23744235.2020.1810858
32. We produced the mask and carried out subjective testing on a user in a typical workplace setting; we demonstrated that the mask was form-fitting, customizable, washable, and could be worn continuously and routinely over extended periods of time by individuals and therefore could serve as an effective means to reduce the harm from SARS-CoV-2: https://www.tandfonline.com/doi/abs/10.1080/00405000.2020.1805971
33. In the meanwhile, reducing dispersion through simple measures, such as surgical masks and careful fitting of the interfaces and sealing of the circuit on supported patients are strongly recommended: https://link.springer.com/article/10.1007/s00134-020-06314-w
34. META-ANALYSIS: “The results of this systematic review and meta-analysis support the conclusion that wearing a mask could reduce the risk of COVID-19 infection.” — https://www.ajicjournal.org/article/S0196-6553(20)31043-9/fulltext
35. META-ANALYSIS: “Masks protect HCWs and other populations against respiratory viral infection.” — https://www.sciencedirect.com/science/article/abs/pii/S1477893920302301
36. META-ANALYSIS: Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253999/
37. In conclusion, in the face of a pandemic, the search for perfect evidence may be the enemy of good policy. As with parachutes for jumping out of aeroplanes,38 it is time to act without waiting for randomised controlled trial evidence.39 A recently posted preprint of a systematic review came to the same conclusion.40 Masks are simple, cheap, and potentially effective. We believe that, worn both in the home (particularly by the person showing symptoms) and also outside the home in situations where meeting others is likely (for example, shopping, public transport), they could have a substantial impact on transmission with a relatively small impact on social and economic life. — https://www.bmj.com/content/369/bmj.m1435
38. Simple and low‐cost interventions would be useful for reducing transmission of epidemic respiratory viruses — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6993921/
39. “The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza.” — https://pubmed.ncbi.nlm.nih.gov/32167245/
40. META-ANALYSIS: Effectiveness of N95 respirators versus surgical masks
    in protecting health care workers from acute respiratory
    infection: a systematic review and meta-analysis: https://www.cmaj.ca/content/cmaj/188/8/567.full.pdf
41. An evidence review that supports mask-wearing with over 110 references. ur review of the literature offers evidence in favour of widespread mask use as source control to reduce community transmission: Nonmedical masks use materials that obstruct particles of the necessary size; people are most infectious in the initial period postinfection, where it is common to have few or no symptoms; nonmedical masks have been effective in reducing transmission of respiratory viruses, and places and periods mask usage is required or widespread have shown substantially lower community transmission. https://www.pnas.org/content/118/4/e2014564118
42. Uni of Tokyo study examining mask efficacy https://journals.asm.org/doi/10.1128/mSphere.00637-20
43. “The study results shed light on the importance of using masks by individuals infected with SARS-CoV-2 and show that different types of masks can help block viral transmission. Moreover, our findings also reinforce the importance of using masks as a preventive measure against viral transmission, regardless of the type of mask used, in addition to social distancing and personal hygiene measures.” https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0264389
44. “Given the efficacy of facemask use as a strategy of respiratory infection control, the policymakers
45. “Should encourage facemask use among the general population for health protection” https://www.nature.com/articles/s41398-022-01814-3
46. RCT: 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 — https://pubmed.ncbi.nlm.nih.gov/22280120/
47. RCT: Hand hygiene and facemasks seemed to prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset. These findings suggest that nonpharmaceutical interventions are important for mitigation of pandemic and interpandemic influenza.” https://pubmed.ncbi.nlm.nih.gov/19652172/
48. “Modeling studies, including this analysis, have estimated how face masks can reduce transmission of SARS-CoV-2 and make a major impact at the population level, even with varying levels of adherence and effectiveness of masks. Multiple public health interventions are needed to reduce the transmission of SARS-CoV-2 and, as our analysis shows, robust use of face masks is an important contributor. Face masks of various materials have the potential to substantially reduce transmission in the SARS-CoV-2 pandemic, depending on the type and fit of the mask and the percentage of adoption in the population. Furthermore, by attempting a more exact quantitation of the impact of masking, studies like this can show, for example, that for highly contagious new variants, such as the Delta and Omicron variants of concern, masks alone are not enough to contain the outbreak, and other control strategies are needed (e.g. social distancing, hand washing, and vaccination). Public outreach and policies encouraging mask-wearing, especially highly efficacious masks such as N95 and KF94, need to be encouraged along with other prevention strategies. In fact, this study suggests that even the imperfect use of masks over the course of the pandemic has likely reduced both cases and deaths significantly.” https://www.nature.com/articles/s41598-022-11934-x
49. “We found substantial value in continuing face mask wearing 2–10 weeks beyond the achievement of target vaccination coverage thresholds to reduce residual SAR-CoV-2 transmission.” https://www.thelancet.com/article/S2468-2667(22)00040-8/fulltext
50. RCT: The golden standard of studies we have is an RCT from Bangladesh, where masks do indeed reduce the spread of viral transmission. The study, which involved more than 342,000 adults, is the largest randomized trial ever conducted on mask usage. A randomized trial of community-level mask promotion in rural Bangladesh during the COVID-19 pandemic shows that the intervention increased mask usage and reduced symptomatic SARS-CoV-2 infections, demonstrating that promoting community mask-wearing can improve public health. https://www.science.org/doi/10.1126/science.abi9069
51. The Morbidity and Mortality Weekly Report (MMWR) from the CDC shared that counties without school mark requirements have experienced larger increases in pediatric COVID-19 cases after the start of school. Therefore, the CDC continues to recommend that schools require universal indoor mask use for students, staff, and others entering the building for grades K-12. https://www.cdc.gov/mmwr/volumes/70/wr/mm7039e1.htm
52. Hong Kong study showed masking was very effective at reducing transmission of alpha coronaviruses. https://www.nature.com/articles/s41591-020-0843-2
53. Moreover, high compliance and correct use of masks is important to ensure the effectiveness of universal masking in reducing the reproduction number for COVID-19. https://www.science.org/doi/10.1126/science.abg6296
54. In fact, this study suggests that even the imperfect use of masks over the course of the pandemic has likely reduced both cases and deaths significantly. https://www.nature.com/articles/s41598-022-11934-x#Sec8
55. This report from an international research team made up of a number of MD’s and other specialists, reviews the data available on cloth masks and concludes that cloth masks worn by the public will reduce COVID-19 transmission rates, and furthermore, those benefits outweigh any risks that may be brought about by wearing masks (such as improper use). https://www.acpjournals.org/doi/10.7326/M20-2567
56. META-ANALYSIS: This systematic review and meta-analysis suggests that several personal protective and social measures, including handwashing, mask-wearing, and physical distancing are associated with reductions in the incidence covid-19. Public health efforts to implement public health measures should consider community health and sociocultural needs, and future research is needed to better understand the effectiveness of public health measures in the context of covid-19 vaccination. https://www.bmj.com/content/375/bmj-2021-068302
57. Wearing a face mask was a protective factor against influenza infection. We recommend a more comprehensive intervention study to accurately estimate this effect. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3810906/
58. The results demonstrated limitations of surgical masks in this context, although they are to some extent protective. Context: this study was from May 2013, but still shows masks back then with limited data did protect against transmission. https://pubmed.ncbi.nlm.nih.gov/23498357/
59. Wearing face masks may reduce primary respiratory infection risk, probably by 6–15%. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7730486/
60. N95 respirator use was associated with fewer viral infectious episodes for healthcare workers compared with surgical masks. The N95 respirator was most effective in reducing the risk of a viral infection in the hospital setting from the SARS-CoV 1 and 2 viruses compared to the other viruses included in this investigation. https://pubmed.ncbi.nlm.nih.gov/34746923/
61. SYSTEMATIC REVIEW: The study suggests that community mask use by well people could be beneficial, particularly for COVID-19, where transmission may be pre-symptomatic. https://www.sciencedirect.com/science/article/pii/S0020748920301139?via%3Dihub
62. This study shows how different types of homemade cloth masks impact respiratory droplet travel. They tested different types of cloth-made masks against emulated coughs and sneezes. All worked to varying degrees. They note that issues like leakage happen when improperly worn, but that nevertheless, homemade cloth masks significantly reduce the distance travelled by expelled particles, and that they are especially effective in stopping larger respiratory droplets, which constitute the majority of the total volume of ejected respiratory fluid. https://aip.scitation.org/doi/10.1063/5.0016018
63. As a conclusion, the recent evidence in COVID-19 pandemic is consistent with the previous studies which have shown association between face mask use and decreased risk of viral infections, and medical face mask use should be encouraged both for the community and healthcare facilities along with other infection control measures such as hand hygiene, during outbreaks when there is widespread community transmission. https://journals.tubitak.gov.tr/medical/vol51/iss7/12/
64. Regardless of the type, setting, or who wears the face mask, it serves primarily a dual preventive purpose; protecting oneself from getting viral infection and protecting others. Therefore, if everyone wears a face mask in public, it offers a double barrier against COVID-19 transmission. https://pubmed.ncbi.nlm.nih.gov/33313575/
65. META-ANALYSIS: It can plausibly be assumed that consistent use of masks covering the mouth and nose can play an important role in containing the spread of SARSCoV- 2. https://www.aerzteblatt.de/int/archive/article/217467
66. Face masks are therefore strongly recommended also outdoors, especially under cold weather conditions, not only as a physical barrier against the transmission of SARS-CoV-2, but also to prevent the rapid cooling of the nasal mucosa and the inhibition of the human innate defense of the upper airways. https://www.mdpi.com/1660-4601/18/6/3214
67. A total of 820 interviewees were included in the analysis and 53.3% of them responded that they wore masks. Non-mask users were infected at a rate of 16.4%, while mask users were infected at a rate of 7.1%. Those who wore masks were infected at a rate of 0.4 times that of those who did not wear masks. (RR = 0.4, 95%CI = 0.3–0.6; Adjusted RR = 0.6, 95%CI = 0.3–0.9). These findings implied that COVID-19 could be avoided to a certain degree by wearing a mask. https://www.mdpi.com/1660-4601/18/17/9131
68. These observations directly demonstrate that wearing of surgical masks or KN95 respirators, even without fit-testing, substantially reduce the number of particles emitted from breathing, talking, and coughing. While the efficacy of cloth and paper masks is not as clear and confounded by shedding of mask fibers, the observations indicate it is likely that they provide some reductions in emitted expiratory particles, in particular the larger particles (> 0.5 μm). https://www.nature.com/articles/s41598-020-72798-7#Sec12
69. CASE-CONTROL: Our findings support consistent wearing of masks, handwashing, and social distancing to protect against COVID-19. https://wwwnc.cdc.gov/eid/article/26/11/20-3003_article
70. cloth face masks are a preventive measure with moderate efficacy in preventing the dissemination of respiratory infections caused by particles with the same size or smaller than those of SARS-CoV-2. The type of fabric used, number of layers and frequency of washings influence the efficacy of the barrier against droplets. https://www.scielo.br/j/rlae/a/rwW9ptCZ9sFmFVxDbLzxHpM/abstract/?lang=en
71. As mentioned before, mask-wearing is still a key strategy for preventing airborne diseases and hence cannot be easily replaced. As easily available alternatives, cloth masks, and 3D-printed masks are discussed along with their advantages and disadvantages. Although most of their filtration efficiencies are not as high as 95% required in commercial face masks and respirators, they can help alleviate the current critical shortage and provide some protection against the spread of the virus. https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202102189
72. This study presents evidence that universal masking of health care workers and patients helps reduce transmission of SARS-CoV-2. The study presents data that shows after universal masking policies were put in place, cases of COVID-19 declined. https://jamanetwork.com/journals/jama/fullarticle/2768533

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