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Do face masks work? Here are 49 scientific studies that explain why they practise

past: Suzannah Kolbeck, BestReviews Staff

Posted: Aug 7, 2021 / 01:48 PM CDT / Updated: Dec 23, 2021 / x:08 AM CST

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AUSTIN (KXAN) — Since the beginning of the historic COVID-nineteen pandemic, one of the most hotly debated subjects has been about masks and whether they actually help slow the spread of the disease. Now, as omicron cuts its mode across the world, the question is back on people's minds.

At the onset of the pandemic, there was slim evidence to either bear witness or disprove the effectiveness of mask-wearing to slow the spread of this particular coronavirus considering, plain, COVID-19 was a new disease. Additionally, there was lilliputian inquiry focusing on respiratory disease manual during a global pandemic of COVID-19'southward magnitude — a once-in-a-lifetime worldwide disaster. Naturally, there was little data to go along about the efficacy of mask-wearing during these verbal circumstances.

This lack of information was perhaps confusing for many but millions in the scientific community quickly jumped to assist the globe understand this illness improve. They built upon years of existing data on coronaviruses and communicable diseases. While researchers of all 49 studies listed below acknowledge there'due south still much more data to be explored, they have all acknowledged the efficacy of mask-wearing to some caste at slowing the spread of COVID-19.

Researchers of 1 study urge people not to infer when reading studies: "Diverse authors have justified not wearing masks on four master grounds. Firstly, they claim that there is limited evidence that they are constructive. The starting time argument tin be challenged on the grounds that absence of show is not evidence of absence."

Reasons for mask hesitancy and doubt include alien information from wellness officials, political biases and cultural unfamiliarity (studies showed mask-wearing was lower in countries where face masking to foreclose affliction was not equally common as in others). While studies disputing masking claims practise be — as is the nature of scientific research — in researching this piece, the bulk explored for this article appeared to conclude either in the affirmative or that more information was needed.

Through the writing of this commodity, efforts were made to exist transparent about publication dates, sources, data sets, and when findings that were critical of mask-wearing appeared. Where they arose, they were included and we worked to give them context.

Below, observe 49 studies (some awaiting peer review) which show the effectiveness of masking.

Peer-reviewed studies:

1. Researchers (including a CDC doctor) for a February 2021 commodity published past the Journal of the American Medical Clan reviewed data from 10 previous studies conclude mask wearing essentially reduces spread. They write that wearing a cloth mask can reduce transmission of exhaled droplets from infected wearers into the air by around 50% to 70%. Additionally, masks were shown to help preclude uninfected wearers from inhaling large respiratory droplets. Overall, the authors plant mask wearing's master benefit is source command, which protects others by reducing the number of respiratory droplets released, rather than respiratory protection, which protects the wearer. Peer reviewed.
   
2. Universal mask adoption for people when in public is recommended by the authors of the "An evidence review of face up masks confronting COVID-nineteen," first published in January by Proceedings of the National Academy of Sciences of the U.Southward. Researchers poured over at least 150 other studies, models and findings to draw their conclusion: "The bachelor evidence suggests that well-nigh-universal adoption of nonmedical masks when out in public, in combination with complementary public wellness measures, could successfully reduce virus reproduction levels to below ane, thereby reducing customs spread if such measures are sustained." Additionally, they posit that mask wearing mandates could add $1 trillion to the U.S. Gdp by preventing business closures. Peer reviewed.
   
3. A loftier-speed laser-low-cal video experiment in The New England Journal of Medicine caused oral fluid droplets to appear every bit flashes in the light. When observed, between 227 and 347 oral fluid aerosol flashed when participants said the words "stay salubrious" without a mask. When the aforementioned phrase was spoken with a mask, "the flash count remained shut to background level." Peer reviewed.
   
4. A June 2020 University of Iowa study published in the Health Diplomacy medical journal estimated over 200,000 COVID-xix cases were prevented in May after masking was mandated in several states. For this experiment, researchers used data analysis and models to measure customs spread before and afterward a mask mandate was enacted. Data found that within 1-5 days after a mandate was issued, daily case rates dropped most i percentage bespeak. Inside 21 or more days, they dropped 2. Peer reviewed.
   
5. A symptomatic traveler with a dry coughing traveled from Wuhan, China, to Toronto, Canada, while wearing a mask, Canadian Medical Association Journal researchers reported in an April 2020 response to a Feb 2020 study. None of the 25 passengers considered "close contacts" aboard the flight contracted the virus. This study indicated that droplet transmission was likely more prevalent than airborne manual. Peer reviewed.
   
6. A June 2020 study in medical journal The Lancet reviewed 172 other studies from 16 countries and plant that while unlike masks offer different effectiveness, masks overall event in a "large reduction in take a chance of infection." Peer reviewed.
   
7. Research in the journal Science addressed ane key merits by mask opponents: that masks don't work because they can yet allow quite a fleck of respiratory thing through. The study explains, nonetheless, that the amount of particles that can come through a mask are dependent on environment and how infected a certain area is. For example, a highly infected group of individuals in a airtight space will upshot in more particles being present overall, including through a mask. Nevertheless, face masks were establish to finer limit probability of COVID-19 transmission. Peer reviewed.
   
8. A study published in the International Journal of Nursing Studies establish that out of a full of 19 randomized controlled trials of communities, masks were effective — even without hand washing. Peer reviewed.
   
9. Authors of a Scientific discipline Advances periodical written report plant that some masks — particularly neck gaiters — could disperse big droplets into smaller, more airborne droplets. However, surgical masks, cotton fiber masks and bandanas were found to cause a reduction in transmission and a pregnant delay between when they left one person's oral cavity and when they were detected. Peer reviewed.
   
10. An article in the medical periodical Respirology concluded (based on 10 previous studies and information) says while questions remain, there are "a range of reasons to abet public mask wearing." Authors noted that while masks protect wearers from droplets more airborne particles, studies of influenza spread show masks are virtually 40-95% efficient. While they believe more data is even so needed, they conclude that although material masks are inferior to medical masks, they're "certainly meliorate than no masks at all." Peer reviewed.
    
11. Models created past the authors of a January 2021 study in the Frontiers in Medicine journal indicated wearing face masks showed favorable outcomes in reducing infection rates. Most importantly, mathematical models indicated a large subtract in mortality when population mask coverage was about-universal. This was true even if mask blazon were less effective types. Peer reviewed.
    
12. A November 2020 commodity published in the Environmental Pollution periodical ended mask wearing is constructive at preventing contact, droplet and possibly airborne transmission of COVID-19. Based on their research — through review of existing data — they urged government officials to further accent the importance of masking. Peer reviewed.
    
13. An October 2020 study in Extreme Mechanics Messages establish that cloth face up coverings, specially masks with multiple layers, take over 70% blocking efficiency. Multiple-layered fabric was found to terminate droplets with more than 94% efficiency, which is equitable to that of medical masks. Peer reviewed.
    
14. A scenario in Nature Medicine projected what would happen if each U.S. land implemented and accomplished 95% of public mask utilise — this resulted in the lowest projected cumulative death toll. Nether this scenario, no states reached daily death rates of eight deaths per million. Other projections found that even if lockdowns/restrictions were non mandated, "whatever additional coverage that can be achieved through mask use will save lives." Peer reviewed.
    
15. Authors of the "How effective is a mask in preventing COVID-19 infection?" study published in Medical Devices & Sensors examined transmission of aerosol through various masks, ultimately finding that correctly wearing masks — despite the varying effectiveness of different types — can largely reduce overall risks of infection and boost protection. Peer reviewed.
    
16. Consumer-course masks (material, bandana) with modifications can offer protection that'south almost the exact same or fifty-fifty ameliorate than non-N95 medical masks professionals use. That's co-ordinate to the researchers in a December 2020 study published in JAMA Internal Medicine. Modifications in fit was the main contributor to increased effectiveness, researchers wrote. Peer reviewed.
    
17. The Annals of Internal Medicine published a study indicating that while researchers don't have enough information to rule that material masks stop transmission of respiratory aerosol from coming in through a mask, there'southward "convincing" evidence to say that cloth masks do reduce particles from going out of a mask and contaminating air and surfaces. The researchers explicate: "Every virus-laden particle retained in a mask is non available to hang in the air every bit an droplets or autumn to a surface to exist later picked upwardly by touch." Peer reviewed.
    
18. While authors of a December 2020 Eurosurveillance infectious illness periodical review of 74 sources decided more data and research is needed, they ultimately estimated face up masks to offered up to fifteen% reduction in disease transmission in their sample pool. Peer reviewed.
    
19. The authors of this April 2020 study found that Taiwan recorded merely 348 COVID-19 cases at that time, while Singapore recorded ane,114. Only Taiwan encouraged masking at the onset of the pandemic, according to the Emerging Infectious Diseases-published written report. While researchers say the reduction was "marginal," they believe the reduction could notwithstanding produce substantial results, specially if implemented early on. Researchers acknowledge limitations to the written report, saying a small sample size was used and there was "suboptimal" adherence to mask wearing among participants. They write: "Taiwan had the foresight to create a large stockpile of medical and surgical masks; other countries or regions might now consider doing so as function of future pandemic plans." Peer reviewed.
    
20. In a study in Periodical of Travel Medicine, published by Oxford University, researchers establish that while mask effectiveness varies depending on type and fit, cloth masks were suitable for non-healthcare workers and could prevent transmission of infection, especially during early on onset. The authors argue that a model showed that even if face masks are simply xx% effective and only 25% of the population used them, infection would be reduced by 30%. Peer reviewed.
    
21. A March 2021 report looked at the affect of New York City'southward April 2020 executive order mandating mask wearing for all in public. At that time, NYC was the epicenter of infections in the U.S., the written report published in Journal of Urban Health explains. Results showed that NYC'due south mask mandate prevented 99,517 infections and 7,978 COVID-19 deaths. Additionally, researchers say if the social club had been implemented but ane week earlier than that, 111,475 infections and 9,017 deaths would take been prevented. Peer reviewed.
    
22. This Hong Kong study published in The International Journal of Tuberculosis and Lung Affliction laments the lack of support for masking in Western countries, as many Asian countries take and have normalized mask wearing for decades. The researchers signal to a previous report cited to dispute benefits of face masks — specially cloth masks — considering they're considered far less effective than surgical masks. The authors argue that while cloth masks are less effective than surgical masks, the departure is most 70% versus ninety%, which they say is all the same a "very meaningful benefit." Peer reviewed.
    
23. Authors of a Dec 2020 study published in Future Microbiology felt strongly about their findings on mask fit, which found they significantly reduce particle transmission when worn properly. They write: "Quantitative analysis of the most efficient and constructive confront masks (in terms of both fit and fabric) will undoubtedly help to stem the spread of not simply SAR-CoV-2 but also any disease spread through respiratory particles." Peer reviewed.
    
24. Researchers in this study of efficacy of different materials used for homemade masks found, as expected, unlike materials take different capabilities in preventing transmission. The laboratory written report was performed in Westward China Hospital of Sichuan University in Chengdu, China and published in October 2020 by the PLOS One scientific periodical community. The lab tested various materials and layering for filtration. The study found that while bootleg masks did non meet surgical mask standards, the filtration efficiency and pressure level departure inside did. They write: "…homemade masks using available materials, based on the results of this study, tin minimize the take chances of infection to the maximum extent." Peer reviewed.
    
25. This BMJ-published report from New South Wales, Australia, used simulation scenarios to deduce that when used together, masking, high community testing and contact tracing are effective at controlling COVID-19 manual. The researchers predictions and models lined up pretty closely with how case numbers played out in New South Wales. Peer reviewed.
    
26. Mathematical models were generated based on huge swaths of data for this study published in Nature Communications. These models found: 1) Fifty-fifty limited distribution of masks offer merely 25% protection and containment would result in significant drop in death rates, ii) Even if only ten% of people used the masks offering 25% protection, the death rate would drop 5%, 3) If people used homemade masks that offered even 5% protection and containment, decease rates would drib from two.5 to ii.26 percent points. Places requiring public masking could also expect a 3-v% reduction in deaths, researchers write. Peer reviewed.
    
27. In this study published in the European Respiratory Journal, researchers examined data from several countries to determine the differences in spread amongst those who masked and those who largely didn't. They urge lawmakers and residents to heed mask guidelines, as it's a favorable culling to shutdowns and prolonged social distancing. The authors write: "… We strongly support the utilize of cloth masks equally a unproblematic, economical and sustainable alternative to surgical masks equally a means of source control for full general community use, so that disposable surgical masks and N95 respirators can be reserved for utilize in healthcare facilities." Peer reviewed.
    
28. A September 2020 study published by the Clan for Psychological Science reviewed several previous studies to determine why many people refuse or resist doing so when, they believe, face masks and social distancing have been proven to help slow affliction spread. Researchers of the report, which centered on empathy, reviewed many previous studies to come to the what before examining the why. Peer reviewed.
    
29. Using data from 15 previous studies, researchers in this The Lancet-published study write: "This study supports universal face mask utilise, because masks were equally effective in both health-care and community settings when adjusted for type of mask use." While the authors acknowledge that surgical and N95 masks are more than effective than fabric masks, data indicate universal mask wearing can reduce the rate of infection, fifty-fifty with moderately constructive ones. Additionally, researchers cite data showing mask wearing in Beijing homes prevented secondary transmission, if worn earlier symptoms appear. Peer reviewed.
    
30. The Beijing report cited in #38 was published in May 2020 by BMJ Global Health — information technology followed 335 people in 124 families that had at least one family member with a confirmed COVID-19 instance. Authors found that after nearly a month in the same household, face mask use by all parties earlier symptom development was 79% effective in manual reduction. Peer reviewed.
    
31. This written report published in the Emerging Infectious Diseases medical journal concluded that while cloth masks are inferior to surgical masks and shouldn't exist used by healthcare workers, they are a suitable option for community use. Fit and cloth are key, researchers write, indicating that fabrics with high thread count and fine weave should be used — in addition to several layers of the material. Peer reviewed.
    
32. These New York University Abu Dhabi researchers examined the resistance of mask wearing in Spain during the early stages of the pandemic. Hither, while exploring how attitudes and biases touch on decisions to clothing masks, explain that many still resist "despite growing prove of the effectiveness of face mask employ against transmission of respiratory viruses." Based on their inquiry, the authors urged governments to create programs to improve mask-wearing compliance. Peer reviewed.
    
33. A Vietnamese study published in the Periodical of Community Health this yr took a wait at mask utilise among academy students. Researchers noted Vietnam's strict mitigation policies during the pandemic, especially given its proximity to Communist china, helped keep case numbers depression (about 28 cases per 10 million people). Measures including mandatory masking in public places — and a monetary fine of about $thirteen The states — led to the successful containment of the coronavirus, researchers write. Again, while surgical masking is the preferred method, researchers urge mask employ and community instruction on their importance. Peer reviewed.
    
34. This January 2021 report published in Journal of Econometrics used robust models, experiments and information sets to review how further masking during the pandemic'southward onset may take prevented infections and deaths. They conclude that their analysis "robustly indicates" face mask mandates take reduced the spread of COVID-nineteen. They explain that if all U.Southward. states had implemented mandatory masking policies on March 14, 2020, the cumulative death toll by the terminate of May would have been about 19% to 45% smaller — or about nineteen,000 to 47,000 saved lives. Peer reviewed.
    
35. But last calendar month, research published on scholarly site PLOS One examined the "substantial" pass up in new COVID-nineteen cases when mask mandates began among a surge in Melbourne, Commonwealth of australia. Using models and logarithm information assay, it's estimated that mask usage in public spaces rose from around 43% to 97% — resulting in a plunge in virus reproduction and new cases. The authors say they strongly support mask usage in communities. Peer reviewed.
    
36. "Of Masks and Methods," published in March in Annals of Internal Medicine, explored how the way masks are worn and implemented affect how effective they are. Researchers examined observational studies and other experiments to conclude that customs mask utilize, especially if widespread, correlates to reduced risk for COVID-xix. They write: "Beyond all analyses odds ratios were approximately 0.8, consistent with a 20% reduction in incident SARS-CoV-two infection if masks are recommended… Multiple observational studies have documented an clan between mask mandates and reduced COVID-19 incidence." Peer reviewed.
    
37. This Irish gaelic written report appearing in scientific periodical publisher MDPI observed the transmission of particles through various mask materials to determine filtration, how porous they were and how much they resist airflow (amid other factors). Using mathematical models, statistical data and historical data, they found masks to be an overall effective and necessary tool for the foreseeable time to come. They explicate that every bit advancements in material occur — including many existing antimicrobial fabrics — masks volition prove even more effective. They write: "Current materials used in production including not-woven fibrous substances have been in use since the beginning of the 20th century and take been shown to be still sufficiently viable in their use." Peer reviewed.
    
38. A February 2021 written report from Ethiopia and published in Risk Management and Healthcare Policy medical journal combed through databases and other COVID-19 writings to conclude that universal face up mask use can contribute to community containment if properly used and available equally needed. Peer reviewed.
    
39. This Feb 2021 JAMA-published study examined several other studies and created a table of different populations around the globe and how their masking employ affected spread. They constitute: "When masks are worn and combined with other recommended mitigation measures, they protect not merely the wearer but too the greater community." Further, they explain that every bit mutations emerge, masking volition be fifty-fifty more of import. Peer reviewed.
    
40. Echoing other findings, the dr./researcher behind this December 2020 Wisconsin Medical Periodical review used over 88 scholarly references to aggregate his ultimate conclusion that the bulk of mask wearing works to control customs spread. The author notes that while a mask tin can just protect wearers from infection to a certain extent, they tin can help control the viral load they're exposed to and thus, the severity of their infection. Peer reviewed.
    
41. This May 2021 Medical Decision Making analysis used models to exam the ability of masks to slow the spread of COVID-19 during an initial outbreak and an uprising. The authors used over 50 sources to decide that even with moderately effective masking "it is evident that mask effectiveness significantly affects transmission." The researchers recommend masking until at least widespread vaccination occurs. Peer reviewed.

Peer-review pending

1. Researchers in this study carried out several simulations where one infected person was put into a population of other participants who were susceptible. Mask wearing amidst the uninfected was gradually increased and a "striking" decrease was seen in the overall number of COVID-nineteen cases. In addition to several other mask-affirming findings, authors of the report published in the Yale Academy-BMJ-affiliated health sciences site MedRxiv, write: "If all individuals move freely and randomly interact with others (i.eastward., 0% SD), the rate of daily infection through the population depends on the percentage of individuals wearing masks."
   
2. University of North Texas Health Scientific discipline Center researchers found in this July 2020 study that "states with an early mask mandate have been able to protect against the June [2020] surge beyond the country. Here, researchers reviewed data — including number of daily case numbers and transmission rate — to decide if local mask mandates affected spread in that state. Observing the 4 counties in the Dallas-Along Worth metroplex, researchers found Dallas and Tarrant counties (both had mask mandates) showed a dramatic driblet in new cases, hospitalizations and ER visits. The other 2 counties, Collin and Denton, did not have mask mandates experienced either growth or marginal subtract.
   
3. A report from the Population Research Institute at the Family Federation of Finland found that if 80% of people in the U.K. masked, information technology would practice more to squelch the pandemic than a full shutdown.
   
4. This Malaysian observational report tracked mask utilise among patients being admitted into hospitals. They ended that all-encompassing use of facemasks could help mitigate impact and more work is needed to make certain people are correctly wearing them.
   
5. The U.S. Ecology Protection Agency (EPA) performed testing of various face up masks — while effectiveness varied, certain textile masks were constitute to exist fifty-fifty meliorate than medical-grade masks. All masks were plant to be effective at stopping transmission at some level.
   
6. A late 2020 written report looking at COVID-19 transmission in Georgia school districts found that schools in the state that required masks to be worn had a 37% lower incidence of COVID-xix amidst teachers and staff than those that didn't. The study, published equally function of the CDC's Morbidity and Mortality Weekly Report, led researchers to recommend mask use for both adults and children during in-person learning.
   
7. Researchers at the European Centre for Disease Prevention and Control found that while mask types offer different degrees of protection and said they think more data is needed, they ultimately recommended mask wearing equally a "non-pharmaceutical intervention."
   
8. This March study included in the CDC's Morbidity and Mortality Weekly Report indicates that county-level COVID-nineteen cases and death rates dropped increasingly in the 20 days following a mask mandate in that canton. Mandates were associated with 0.5 percentage rate drops in the beginning 1-20 days and 1.1-1.eight percentage point drops between 21-100 days. Researchers highly recommended mask mandates in addition to other mitigation efforts post-obit their work.

Retracted/disputed claims

1. A "inquiry letter of the alphabet" published past JAMA Pediatrics merely one month agone has since been retracted due to claims that the authors couldn't dorsum up their findings. The letter of the alphabet, "Experimental Assessment of Carbon Dioxide Content in Inhaled Air With or Without Confront Masks in Salubrious Children: A Randomized Clinical Trial," claimed that toxic amounts of carbon dioxide were "measured" inside of face up masks worn by children. The claim was touted by Pull a fast one on News host Tucker Carlson in early July and proliferated online, all the same, the scientific community scrutinized the study earlier it was ultimately retracted.
   
2. A Texas A&M study took a look at how COVID-19 is transmitted plant people who wore masks prevented a projected 66,000 people in New York City from getting infected in less than 1 month. Based on mathematical analysis, they explained that global statistics showed: "… Wearing of confront masks in public corresponds to the most effective means to preclude interhuman transmission," researchers wrote. This inquiry has been rejected for peer review twice due to ambiguous data, assumptions made by researchers, and uncontrolled factors. One peer who did not approve the findings wrote that while there's "growing evidence" to support masking recommendations, it's all the same too early.
   
3. This Apr 2020 written report published in the Register of Internal Medicine was retracted in July 2020 later on some data was found to be incorrect due to miscalculations, including data showing surgical masks were less constructive than material masks and peradventure led readers to believe surgical masks were ineffective. While researchers requested to right the data, editors insisted the written report be pulled.
   
4. One of the most famous and controversial mask studies is amidst the get-go that was performed during the pandemic. Dubbed "The Danish Written report," or "DANMASK-19", the findings were labeled on social media as proof that cloth and surgical masks don't work. Still, the estimation of its findings has been disputed by many who say information technology ultimately rules "more than information needed" and is "inconclusive." Overall, protection was deemed to exist limited. Moreover, the report's authors also wrote: "[the report] should non be used to conclude that a recommendation for anybody to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the function of masks in source control of SARS-CoV-2 infection."
   
5. Another ofttimes-cited report many say proves masks are inefficient was published in a Jan 2021 issue of Medical Hypotheses and called "Facemasks in the COVID-nineteen era: A health hypothesis." The study concluded that masks — both fabric and medical — were "ineffective." The study circulated on social media with some challenge it originated from Stanford University and/or the National Institutes of Health. Neither is truthful, with Stanford Medicine explaining it strongly supports mask usage.

Follow KXAN's Russell Falcon on Twitter @RussellFalcon for more coronavirus updates.

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