Maintaining at least one meter from others and wearing face masks and eye protection, inside and outside health care settings, can be the best way to reduce the possibility of viral infection or COVID-19 transmission, according to a systematic review and meta-analysis synthesizing all evidence that available from scientific literature, published in Lancet.
However, none of these interventions, even when properly used and combined, provide complete protection from infection, and the authors note that some findings, especially around face masks and eye protection, are supported by evidence of low certainty, without completing randomized trials try to handle COVID-19 for this intervention.
The research carried out to inform this WHO guideline document is the first time researchers have systematically examined the optimal use of these protective measures in the community and health services for COVID-19. The authors say it has direct and important implications for limiting the current COVID-19 pandemic and future waves by informing disease models, and standardizing the definition of who is ‘potentially exposed’ (ie, within 2 meters) for contact tracing.
Many countries and regions have issued conflicting suggestions about physical distance to reduce transmission of COVID-19, based on limited information. In addition, the question of whether masks and eye patches can reduce transmission of COVID-19 in the general population, and what optimal mask use is in health care settings, has been debated during the pandemic.
“Our findings are the first to synthesize all direct information about COVID-19, SARS, and MERS, and provide the best available evidence of optimal use of these general and simple interventions to help” level the curve “and inform pandemic response efforts in society “, said Professor Holger Schünemann of McMaster University in Canada, who co-led the research. “The government and community health community can use our results to provide clear advice for community and health care providers about these protective measures to reduce the risk of infection.”
The best evidence currently available shows that COVID-19 is most commonly spread by respiratory droplets, especially when people cough and sneeze, enter through the eyes, nose, and mouth, either directly or by touching a contaminated surface. At present, despite the consensus that SARS-CoV-2 mainly spreads through large droplets and contacts, debate continues about the role of aerosol spread.
For the current analysis, the international research team conducted a systematic review of 172 observational studies that assessed distance measures, facial masks, and eye protection to prevent transmission between patients with confirmed or possible confirmed COVID-19, SARS, or MERS infections as well as those who close to them (eg caregivers, families, health care workers), until 3 May 2020.
Estimates collected from 44 comparative studies involving 25,697 participants were included in the meta-analysis. Of these, 7 studies focused on COVID-19 (6,674 participants), 26 on SARS (15,928), and 11 on MERS (3,095).
The COVID-19 study included in the analysis consistently reported benefits for all three interventions and had findings similar to those of the SARS and MERS studies.
Analysis of data from nine studies (across SARS, MERS and COVID-19, including 7,782 participants) who looked at physical distance and virus transmission found that maintaining a distance of more than one meter from others was associated with a much lower risk of infection compared to less than one meters (the risk of infection when an individual stands more than one meter from an infected person is 3% vs. 13% if in one meter), however, modeling suggests that for each extra meter further up to three meters, the risk of infection or transmission can be halved. The authors note that the certainty of their evidence about physical distance is moderate and that there are no studies that quantitatively evaluate whether distances greater than 2 meters are more effective, although meta-analyzes provide risk estimates.
Thirteen studies (in all three viruses, including 3,713 participants) focusing on eye protection found that face shields, eyeglasses, and eyeglasses were associated with a lower risk of infection, compared with no eye patch (risk of infection or transmission when wearing eye protection was 6). % vs 16% when not wearing eye protection). The authors note that the certainty of the evidence for blindfolds is low.
Evidence from 10 studies (in all three viruses, including 2,647 participants) also found the same benefits for general face masks (the risk of infection or transmission when wearing a mask was 3% vs. 17% when not wearing a mask). The evidence in this study mainly looked at the use of masks in the household and between case contacts, and was also based on evidence of low certainty.
For healthcare workers, N95 and other respirator type masks may be associated with greater protection from virus transmission than surgical masks or the like (eg, reusable cotton or gauze masks 12-16). For the general public, face masks may also be related to protection, even in non-health settings, with disposable surgical masks or those that use cotton lining 12-16. However, the authors note that there is concern that the use of face masks risks diverting supplies from health workers and other nurses with the highest risk for infection.
They also stressed that policy makers need to quickly address the problem of access to face masks to ensure that they are equally available to all. “With respirators such as N95, surgical masks, and eye protection in short supply, and urgently needed by front-line health care workers treating COVID-19 patients, increasing and repurposing production capacity is urgently needed to overcome global deficiencies,” said co-author Dr. Derek Chu, Assistant Professor at McMaster University. “We also believe that solutions must be found to make face masks available to the general public. However, one should be clear that wearing a mask is not an alternative to maintaining physical distance, eye protection or basic actions such as hand hygiene, but might add an additional layer of protection. “
The authors also emphasize the importance of using information about how acceptable, feasible, resource intensive, and equally accessible to all uses of this intervention when making recommendations. “In 24 studies of the three viruses including 50,566 individuals, most participants found this personal protection strategy acceptable, feasible, and convincing, but noted the dangers and challenges including frequent discomfort and facial skin damage, increased difficulty communicating clearly, and perceived reduced empathy from care. providers by those they care for, “said Dr. Sally Yaacoub of the American University of Beruit in Lebanon.
According to co-author Karla Solo of McMaster University in Canada: “Although our results provide evidence of moderate and low certainty, this is the first study that synthesizes all information directly from COVID-19 and, therefore, provides the best current evidence to inform optimal use from this general and simple intervention. “
Apart from these important findings, this review has several limitations including several studies that assess the effects of interventions in non-health settings, and most of the evidence comes from SARS and MERS studies. Finally, the effect of duration of exposure on the risk of transmission was not specifically examined.
Writing in the comment link, lead author Professor Raina MacIntyre (who was not involved in the research) from the Kirby Institute, University of New South Wales in Australia, described the study as an “important milestone”, and wrote, “For health care workers on the COVID ward” 19, respirators must be the minimum standard of care.This study by Chu and colleagues must request a review of all guidelines that recommend medical masks for health care workers who treat COVID patients19. Although medical masks protect, the health and safety of health workers must be the highest priority and the precautionary principle is applied. “
He continued, “[They] also reported that multilayer respirators and masks are more protective than single-layer masks. This finding is very important to inform the proliferation of designs of homemade fabric masks, many of which are single-layered. A well-designed fabric mask must have a waterproof fabric, many layers, and a good face fit … The use of a universal face mask might allow the removal of safe restrictions in a society that wants to resume normal activities and can protect people in the public environment which is crowded and inside the household. “
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