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HomeMy WebLinkAbout022323 NYTimes_ _Mask Mandates Did Nothing_ per gold-standard randomized controlled trials________________________________ ALERT: BE CAUTIOUS This email originated outside the organization. Do not open attachments or click on links if you are not expecting them. ________________________________ https://www.nytimes.com/2023/02/21/opinion/do-mask-mandates-work.html The Mask Mandates Did Nothing. Will Any Lessons Be Learned? The New York Times, Feb. 21, 2023 - By <https://www.nytimes.com/by/bret-stephens>Bret Stephens The <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/full>most rigorous and comprehensive analysis of scientific studies conducted on the efficacy of masks for reducing the spread of respiratory illnesses ­ including Covid-19 ­ was published late last month. Its conclusions, said Tom Jefferson, the Oxford epidemiologist who is its lead author, were unambiguous. "There is just no evidence that they" ­ masks ­ "make any difference," <https://maryannedemasi.substack.com/p/exclusive-lead-author-of-new-cochrane>he told the journalist Maryanne Demasi. "Full stop." But, wait, hold on. What about N-95 masks, as opposed to lower-quality surgical or cloth masks? "Makes no difference ­ none of it," said Jefferson. What about the studies that initially persuaded policymakers to impose mask mandates? "They were convinced by nonrandomized studies, flawed observational studies." What about the utility of masks in conjunction with other preventive measures, such as hand hygiene, physical distancing or air filtration? "There's no evidence that many of these things make any difference." These observations don't come from just anywhere. Jefferson and 11 colleagues conducted the study for <https://www.cochrane.org/>Cochrane, a British nonprofit that is widely considered the gold standard for its reviews of health care data. The conclusions were based on 78 randomized controlled trials, six of them during the Covid pandemic, with a total of 610,872 participants in multiple countries. And they track what has been widely observed in the United States: States with mask mandates fared no better against Covid than those without. No study ­ or study of studies ­ is ever perfect. Science is never absolutely settled. What's more, the analysis does not prove that proper masks, properly worn, had no benefit at an individual level. People may have good personal reasons to wear masks, and they may have the discipline to wear them consistently. Their choices are their own. But when it comes to the population-level benefits of masking, the verdict is in: Mask mandates were a bust. Those skeptics who were furiously mocked as cranks and occasionally censored as "misinformers" for opposing mandates were right. The mainstream experts and pundits who supported mandates were wrong. In a better world, it would behoove the latter group to acknowledge their error, along with its considerable <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9638642/>physical, <https://uwaterloo.ca/news/media/research-suggests-mask-wearing-can-increase-struggles-social>psychological, <https://www.npr.org/2022/01/28/1075842341/growing-calls-to-take-masks-off-children-in-school>pedagogical and <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8866197/>political costs. Don't count on it. In <https://www.youtube.com/watch?v=0y2XV1qox0c&t=4497s>congressional testimony this month, Rochelle Walensky, director of the Centers for Disease Control and Prevention, called into question the Cochrane analysis's reliance on a small number of Covid-specific randomized controlled trials and insisted that her agency's guidance on masking in schools <https://www.reuters.com/world/us/us-cdc-stands-by-k-12-school-masking-guidance-states-relax-rules-walensky-2022-02-08/>wouldn't change. If she ever wonders why respect for the C.D.C. keeps falling, she could look to herself, and resign, and leave it to someone else <https://ncmedsoc.org/cdc-announces-sweeping-changes-to-restore-public-trust/>to reorganize her agency. That, too, probably won't happen: We no longer live in a culture in which resignation is seen as the honorable course for public officials who fail in their jobs. But the costs go deeper. When people say they "trust the science," what they presumably mean is that science is rational, empirical, rigorous, receptive to new information, sensitive to competing concerns and risks. Also: humble, transparent, open to criticism, honest about what it doesn't know, willing to admit error. The C.D.C.'s increasingly mindless <https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/about-face-coverings.html#:%7E:text=At%20All%20COVID%2D19%20Community,by%20local%20or%20state%20authorities.>adherence to its masking guidance is none of those things. It isn't merely undermining the trust it requires to operate as an effective public institution. It is turning itself into an unwitting accomplice to the genuine enemies of reason and science ­ conspiracy theorists and quack-cure peddlers ­ by so badly representing the values and practices that science is supposed to exemplify. It also betrays the technocratic mind-set that has the unpleasant habit of assuming that nothing is ever wrong with the bureaucracy's well-laid plans ­ provided nobody gets in its way, nobody has a dissenting point of view, everyone does exactly what it asks, and for as long as officialdom demands. This is the mentality that once believed that China provided a highly successful model for pandemic response. Yet there was never a chance that mask mandates in the United States would get anywhere close to 100 percent compliance or that people would or could wear masks in a way that would meaningfully reduce transmission. Part of the reason is specific to American habits and culture, part of it to constitutional limits on government power, part of it to human nature, part of it to competing social and economic necessities, part of it to the evolution of the virus itself. But whatever the reason, mask mandates were a fool's errand from the start. They may have created a false sense of safety ­ and thus permission to resume semi-normal life. They did almost nothing to advance safety itself. The Cochrane report ought to be the final nail in this particular coffin. There's a final lesson. The last justification for masks is that, even if they proved to be ineffective, they seemed like a relatively low-cost, intuitively effective way of doing something against the virus in the early days of the pandemic. But "do something" is not science, and it shouldn't have been public policy. And the people who had the courage to say as much deserved to be listened to, not treated with contempt. They may not ever get the apology they deserve, but vindication ought to be enough. --- "No evidence from high quality studies that ... masks make any difference to transmission" --- https://dailysceptic.org/2023/02/06/dr-carl-heneghan-interviews-dr-tom-jefferson-about-his-major-new-study-showing-masks-have-no-clear-effect/ Dr. Tom Jefferson is the lead author of the newly updated <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/full>Cochrane review on the evidence on masks and other physical interventions for combating respiratory viruses like SARS-CoV-2. Following the publication of the review Dr. Jefferson was <https://trusttheevidence.substack.com/p/tte-podcast-physical-interventions#details>interviewed by his colleague, Oxford's Professor Carl Heneghan. TJ: So, a Cochrane review is a study which synthesises all available studies - all that we can find or identity - on a particular topic. It follows a highly structured format and is always preceded by publication of a protocol. All this is to minimise the bias. Also, it is extensively transparent. In this case we are looking at about 300 pages of review. Now, the review called "Physical interventions to interrupt or reduce the spread of respiratory viruses" is called in code A122 for short and I will be using that acronym simply because it is just too long a title. So the protocol was first published in 2006 and then the first version was published in 2007, updated in 2009, 2010, 2011, and then 2020, so this 2023 is the fifth update of this review. And the reason why we update the reviews is they are soon out of date if we don't do that, especially in some fast moving topics. CH: So it's interesting what's happening here is that if I look at this you've sort of updated it for the swine flu pandemic of 2009-2011, and then there was a large gap until now, when you've had two updates within a couple of years. And I think that's quite interesting because there's a lot of interest in the interventions within this review. Let me just say what physical interventions are. They are screening at entry ports, isolation, quarantine, physical distance, personal protection, hand hygiene, face masks, glasses and gargling. That's a lot of interventions but I'm sure most people out of all those will be really interested in terms of the masks results, so I'll come to them later. But first, what did you include differently in this review compared to just two or three years ago, what new studies are included, and what difference has it made? TJ: The original review had randomised and non-randomised evidence, but when we got to 2020 we had 67 trials, it had grown exponentially, with all sorts of physical interventions, so we decided there was no point in looking at low quality evidence which was difficult to interpret and no conclusions could be drawn from, if we had this massive wealth of trials. So in 2020 we went forward only with randomised control trials, and we had 67. We've since added another 11, so we've got 78 in this update. Forty-three trials contribute to the metanalysis, that's the statistical pooling and analysis of the results. So 11 studies added in this update and the total of the participants in the whole review is 610,872, so it is a very huge dataset of randomised data. CH: Interesting, so we've got a significant amount of randomised controlled data so we'll come back to your observational data later. But here's the first result I want to go to, medical and surgical masks compared to no mask. And what you say in the results is that we included 12 trials, and it says that wearing masks in the community probably makes little or no difference to the outcome of influenza-like illness (ILI) or COVID-19-like illness compared to not wearing masks. Now could you just decode what that actually means, because there are lots of Covid-like or influenza-like illness, and what that result means now in the context of this new evidence TJ. The result means that regardless of what pathogen or what presenting symptom there is no evidence from high quality studies that either medical or surgical masks make any difference to transmission, which is the whole point of wearing or not wearing a mask or any of these other interventions like hand-washing. --- Revealing interview with lead author of new Cochrane review --- https://maryannedemasi.substack.com/p/exclusive-lead-author-of-new-cochrane DEMASI: This Cochrane review has caused quite a stir on social media and inflamed the great mask debate. What are your thoughts? JEFFERSON: Well, it's an update from our November 2020 review and the evidence really didn't change from 2020 to 2023. There's still no evidence that masks are effective during a pandemic. DEMASI: And yet, most governments around the world implemented mask mandates during the pandemic... JEFFERSON: Yes, well, governments completely failed to do the right thing and demand better evidence. At the beginning of the pandemic, there were some voices who said masks did not work and then suddenly the narrative changed. DEMASI: That is true, Fauci went on 60 minutes and said that masks are not necessary and then weeks later he changed his tune. JEFFERSON: Same with New Zealand's Chief Medical Officer. One minute he is saying masks don't work, and the next minute, he flipped. DEMASI: Why do you think that happened? JEFFERSON: Governments had bad advisors from the very beginning... They were convinced by non-randomised studies, flawed observational studies. A lot of it had to do with appearing as if they were "doing something." In early 2020, when the pandemic was ramping up, we had just updated our Cochrane review ready to publish...but Cochrane held it up for 7 months before it was finally published in November 2020. Those 7 months were crucial. During that time, it was when policy about masks was being formed. Our review was important, and it should have been out there. DEMASI: What was the delay? JEFFERSON: For some unknown reason, Cochrane decided it needed an "extra" peer-review. And then they forced us to insert unnecessary text phrases in the review like "this review doesn't contain any covid-19 trials," when it was obvious to anyone reading the study that the cut-off date was January 2020. DEMASI: Do you think Cochrane intentionally delayed that 2020 review? JEFFERSON: During those 7 months, other researchers at Cochrane produced some unacceptable pieces of work, using unacceptable studies, that gave the "right answer". DEMASI: What do you mean by "the right answer"? Are you suggesting that Cochrane was pro-mask, and that your review contradicted the narrative. Is that your intuition? JEFFERSON: Yes, I think that is what was going on. After the 7-month delay, Cochrane then published <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.ED000149/full>an editorial to accompany our review. The main message of that editorial was that you can't sit on your hands, you've got to do something, you can't wait for good evidence.... it's a complete subversion of the 'precautionary principle' which states that you should do nothing unless you have reasonable evidence that benefits outweigh the harms. DEMASI: Why would Cochrane do that? JEFFERSON: I think the purpose of the editorial was to undermine our work. DEMASI: Do you think Cochrane was playing a political game? JEFFERSON: That I cannot say, but it was 7 months that just happened to coincide with the time when all the craziness began, when academics and politicians started jumping up and down about masks. We call them "strident campaigners". They are activists, not scientists. DEMASI: That's interesting. JEFFERSON: Well, no. It's depressing. DEMASI: So, the 2023 updated review now includes a couple of new covid-19 studies....the Danish mask study....and the Bangladesh study. In fact, there was a lot of discussion about the Bangladesh mask study which claimed to show some benefit.... JEFFERSON: That was not a very good study because it was not a study about whether masks worked, it was a study about increasing compliance for wearing a mask. DEMASI: Right, I remember there was a <https://trialsjournal.biomedcentral.com/articles/10.1186/s13063-022-06704-z>reanalysis of the Bangladesh study showing it had significant bias....you've worked in this area for decades, you're an expert... JEFFERSON [interjects]... please do not call me an expert. I'm a guy who has worked in the field for some time. That has to be the message. I don't work with models, I don't make predictions. I don't hassle people or chase them on social media. I don't call them names... I'm a scientist. I work with data. David Sackett, the founder of Evidence Based Medicine, once wrote a very famous <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1118019/>article for The BMJ saying that 'experts' are part of the problem. You just have to look at the so-called 'experts' that have been advising government. DEMASI: There were so many silly mask policies. They expected 2yr olds to wear masks, and you had to wear a mask to walk into a restaurant, but you could take it off as soon as you sat down. JEFFERSON: Yes, also the 2- meter rule. Based on what? Nothing. DEMASI: Did you wear a mask? JEFFERSON: I follow the law. If the law says I need to wear one, then I wear one because I have to. I do not break the law. I obey the law of the country. DEMASI: Yeah, same. What would you say to people who still want to wear a mask? JEFFERSON: I think it's fair to say that if you want to wear a mask then you should have a choice, okay. But in the absence of evidence, you shouldn't be forcing anybody to do so. DEMASI: But people say, I'm not wearing a mask for me, I'm wearing it for you. JEFFERSON: I have never understood that difference. Have you? DEMASI: They say it's not to protect themselves, but to protect others, an act of altruism. JEFFERSON: Ah yes. Wonderful. They get the Albert Schweitzer prize for Humanitarianism. Here's what I think. Your overnight experts know nothing. DEMASI (laughs) JEFFERSON: There is just no evidence that they make any difference. Full stop. My job, our job as a review team, was to look at the evidence, we have done that. --- 2023 Cochrane Review itself --- https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/full <https://www.cochranelibrary.com/>Cochrane Database of Systematic Reviews - Intervention Physical interventions to interrupt or reduce the spread of respiratory viruses Tom Jefferson, Liz Dooley, Eliana Ferroni, Lubna A Al-Ansary, Mieke L van Driel, Ghada A Bawazeer, Mark A Jones, Tammy C Hoffmann, Justin Clark, Elaine M Beller Paul P Glasziou, John M Conly Version published: 30 January 2023 https://doi.org/10.1002/14651858.CD006207.pub6 Abstract Background Viral epidemics or pandemics of acute respiratory infections (ARIs) pose a global threat. Examples are influenza (H1N1) caused by the H1N1pdm09 virus in 2009, severe acute respiratory syndrome (SARS) in 2003, and coronavirus disease 2019 (COVID 19) caused by SARS CoV 2 in 2019. Antiviral drugs and vaccines may be insufficient to prevent their spread. This is an update of a Cochrane Review last published in 2020. We include results from studies from the current COVID 19 pandemic. Objectives To assess the effectiveness of physical interventions to interrupt or reduce the spread of acute respiratory viruses. Search methods We searched CENTRAL, PubMed, Embase, CINAHL, and two trials registers in October 2022, with backwards and forwards citation analysis on the new studies. Selection criteria We included randomised controlled trials (RCTs) and cluster RCTs investigating physical interventions (screening at entry ports, isolation, quarantine, physical distancing, personal protection, hand hygiene, face masks, glasses, and gargling) to prevent respiratory virus transmission. Data collection and analysis We used standard Cochrane methodological procedures. Main results We included 11 new RCTs and cluster RCTs (610,872 participants) in this update, bringing the total number of RCTs to 78. Six of the new trials were conducted during the COVID 19 pandemic; two from Mexico, and one each from Denmark, Bangladesh, England, and Norway. We identified four ongoing studies, of which one is completed, but unreported, evaluating masks concurrent with the COVID 19 pandemic. Many studies were conducted during non epidemic influenza periods. Several were conducted during the 2009 H1N1 influenza pandemic, and others in epidemic influenza seasons up to 2016. Therefore, many studies were conducted in the context of lower respiratory viral circulation and transmission compared to COVID 19. The included studies were conducted in heterogeneous settings, ranging from suburban schools to hospital wards in high income countries; crowded inner city settings in low income countries; and an immigrant neighbourhood in a high income country. Adherence with interventions was low in many studies. The risk of bias for the RCTs and cluster RCTs was mostly high or unclear. Medical/surgical masks compared to no masks We included 12 trials (10 cluster RCTs) comparing medical/surgical masks versus no masks to prevent the spread of viral respiratory illness (two trials with healthcare workers and 10 in the community). Wearing masks in the community probably makes little or no difference to the outcome of influenza like illness (ILI)/COVID 19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate certainty evidence. Wearing masks in the community probably makes little or no difference to the outcome of laboratory confirmed influenza/SARS CoV 2 compared to not wearing masks (RR 1.01, 95% CI 0.72 to 1.42; 6 trials, 13,919 participants; moderate certainty evidence). Harms were rarely measured and poorly reported (very low certainty evidence). N95/P2 respirators compared to medical/surgical masks We pooled trials comparing N95/P2 respirators with medical/surgical masks (four in healthcare settings and one in a household setting). We are very uncertain on the effects of N95/P2 respirators compared with medical/surgical masks on the outcome of clinical respiratory illness (RR 0.70, 95% CI 0.45 to 1.10; 3 trials, 7779 participants; very low certainty evidence). N95/P2 respirators compared with medical/surgical masks may be effective for ILI (RR 0.82, 95% CI 0.66 to 1.03; 5 trials, 8407 participants; low certainty evidence). Evidence is limited by imprecision and heterogeneity for these subjective outcomes. The use of a N95/P2 respirators compared to medical/surgical masks probably makes little or no difference for the objective and more precise outcome of laboratory confirmed influenza infection (RR 1.10, 95% CI 0.90 to 1.34; 5 trials, 8407 participants; moderate certainty evidence). Restricting pooling to healthcare workers made no difference to the overall findings. Harms were poorly measured and reported, but discomfort wearing medical/surgical masks or N95/P2 respirators was mentioned in several studies (very low certainty evidence). One previously reported ongoing RCT has now been published and observed that medical/surgical masks were non inferior to N95 respirators in a large study of 1009 healthcare workers in four countries providing direct care to COVID 19 patients. Hand hygiene compared to control Nineteen trials compared hand hygiene interventions with controls with sufficient data to include in meta analyses. Settings included schools, childcare centres and homes. Comparing hand hygiene interventions with controls (i.e. no intervention), there was a 14% relative reduction in the number of people with ARIs in the hand hygiene group (RR 0.86, 95% CI 0.81 to 0.90; 9 trials, 52,105 participants; moderate certainty evidence), suggesting a probable benefit. In absolute terms this benefit would result in a reduction from 380 events per 1000 people to 327 per 1000 people (95% CI 308 to 342). When considering the more strictly defined outcomes of ILI and laboratory confirmed influenza, the estimates of effect for ILI (RR 0.94, 95% CI 0.81 to 1.09; 11 trials, 34,503 participants; low certainty evidence), and laboratory confirmed influenza (RR 0.91, 95% CI 0.63 to 1.30; 8 trials, 8332 participants; low certainty evidence), suggest the intervention made little or no difference. We pooled 19 trials (71, 210 participants) for the composite outcome of ARI or ILI or influenza, with each study only contributing once and the most comprehensive outcome reported. Pooled data showed that hand hygiene may be beneficial with an 11% relative reduction of respiratory illness (RR 0.89, 95% CI 0.83 to 0.94; low certainty evidence), but with high heterogeneity. In absolute terms this benefit would result in a reduction from 200 events per 1000 people to 178 per 1000 people (95% CI 166 to 188). Few trials measured and reported harms (very low certainty evidence). We found no RCTs on gowns and gloves, face shields, or screening at entry ports. Authors' conclusions The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions. There were additional RCTs during the pandemic related to physical interventions but a relative paucity given the importance of the question of masking and its relative effectiveness and the concomitant measures of mask adherence which would be highly relevant to the measurement of effectiveness, especially in the elderly and in young children. There is uncertainty about the effects of face masks. The low to moderate certainty of evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect. The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness, and although this effect was also present when ILI and laboratory confirmed influenza were analysed separately, it was not found to be a significant difference for the latter two outcomes. Harms associated with physical interventions were under investigated. There is a need for large, well designed RCTs addressing the effectiveness of many of these interventions in multiple settings and populations, as well as the impact of adherence on effectiveness, especially in those most at risk of ARIs. Authors' conclusions Implications for practice The evidence summarised in this review on the use of masks is largely based on studies conducted during traditional peak respiratory virus infection seasons up until 2016. Two relevant randomised trials conducted during the COVID 19 pandemic have been published, but their addition had minimal impact on the overall pooled estimate of effect. The observed lack of effect of mask wearing in interrupting the spread of influenza like illness (ILI) or influenza/COVID 19 in our review has many potential reasons, including: poor study design; insufficiently powered studies arising from low viral circulation in some studies; lower adherence with mask wearing, especially amongst children; quality of the masks used; self contamination of the mask by hands; lack of protection from eye exposure from respiratory droplets (allowing a route of entry of respiratory viruses into the nose via the lacrimal duct); saturation of masks with saliva from extended use (promoting virus survival in proteinaceous material); and possible risk compensation behaviour leading to an exaggerated sense of security (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0272>Ammann 2022; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0279>Brosseau 2020; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0281>Byambasuren 2021; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0016>Canini 2010; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0282>Cassell 2006; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0290>Coroiu 2021; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0048>MacIntyre 2015; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0351>Rengasamy 2010; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0256>Zamora 2006). Our findings show that hand hygiene has a modest effect as a physical intervention to interrupt the spread of respiratory viruses, but several questions remain. First, the high heterogeneity between studies may suggest that there are differences in the effect of different interventions. The poor reporting limited our ability to extract the information needed to assess any 'dose response' relationship, and there are few head to head trials comparing hand hygiene materials (such as alcohol based sanitiser or soap and water). Second, the sustainability of hand hygiene is unclear where participants in some studies achieved 5 to 10 hand washings per day, but adherence may have diminished with time as motivation decreased, or due to adverse effects from frequent hand washing. Third, there is little evidence about the effectiveness of combinations of hand hygiene with other interventions, and how those are best introduced and sustained. Finally, some interventions were intensively implemented within small organisations, and involved education or training as a component, and the ability to scale these up to broader interventions is unclear. Our findings with respect to hand hygiene should be considered generally relevant to all viral respiratory infections, given the diverse populations where transmission of viral respiratory infections occurs. The participants were adults, children and families, and multiple congregation settings including schools, childcare centres, homes, and offices. Most respiratory viruses, including the pandemic SARS CoV 2, are considered to be predominantly spread via respiratory particles of varying size or contact routes, or both (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0372>WHO 2020c). Data from studies of SARS CoV 2 contamination of the environment based on the presence of viral ribonucleic acid and infectious virus suggest significant fomite contamination (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0327>Lin 2022; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0341>Onakpoya 2022b; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0342>Ong 2020; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0377>Wu 2020). Hand hygiene would be expected to be beneficial in reducing the spread of SARS CoV 2 similar to other beta coronaviruses (SARS CoV 1, Middle East respiratory syndrome (MERS), and human coronaviruses), which are very susceptible to the concentrations of alcohol commonly found in most hand sanitiser preparations (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0215>Rabenau 2005; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0372>WHO 2020c). Support for this effect is the finding that poor hand hygiene, despite the use of full personal protective equipment (PPE), was independently associated with an increased risk of SARS CoV 2 transmission to healthcare workers in a retrospective cohort study in Wuhan, China in both a high risk and low risk clinical unit for patients infected with COVID 19 (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0350>Ran 2020). The practice of hand hygiene appears to have a consistent effect in all settings, and should be an essential component of other interventions. The highest quality cluster RCTs indicate that the most effect on preventing respiratory virus spread from hygienic measures occurs in younger children. This may be because younger children are least capable of hygienic behaviour themselves (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0060>Roberts 2000), and have longer lived infections and greater social contact, thereby acting as portals of infection into the household (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0336>Monto 1969). Additional benefit from reduced transmission from them to other members of the household is broadly supported by the results of other study designs where the potential for confounding is greater. Routine long term implementation of some of the interventions covered in this review may be problematic, particularly maintaining strict hygiene and barrier routines for long periods of time. This would probably only be feasible in highly motivated environments, such as hospitals. Many of the trial authors commented on the major logistical burdens that barrier routines imposed at the community level. However, the threat of a looming epidemic may provide stimulus for their inception. Implications for research Public health measures and physical interventions can be highly effective to interrupt the spread of respiratory viral infections, especially when they are part of a structured and co ordinated programme that includes instruction and education, and when they are delivered together and with high adherence. Our review has provided important insights into research gaps that need to be addressed with respect to these physical interventions and their implementation and have been brought into a sharper focus as a result of the COVID 19 pandemic. The 2014 WHO document 'Infection prevention and control of epidemic and pandemic prone acute respiratory infections in health care' identified several research gaps as part of their GRADE assessment of their infection prevention and control recommendations, which remain very relevant (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0368>WHO 2014). Research gaps identified during the course of our review and the <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0368>WHO 2014 document may be considered from the perspective of both general and specific themes. A general theme identified was the need to provide outcomes with explicitly defined clinical criteria for acute respiratory infections (ARIs) and discrete laboratory confirmed outcomes of viral ARIs using molecular diagnostic tools which are now widely available. Our review found large disparities between studies with respect to the clinical outcome events, which were imprecisely defined in several studies, and there were differences in the extent to which laboratory confirmed viruses were included in the studies that assessed them. Another general theme identified was the lack of consideration of sociocultural factors that might affect adherence with the interventions, especially those employed in the community setting. A prime example of this latter point was illustrated by the observations of the use of masks versus mask mandates during the COVID 19 pandemic. In addition, the cost and resource implications of the physical interventions employed in different settings would have important relevance for low to middle income countries. Resources have been a major issue with the COVID 19 pandemic, with global shortages of several components of PPE. Several specific research gaps related to physical interventions were identified within the <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0368>WHO 2014 document and are congruent with many of the findings of this 2022 update, including the following: transmission dynamics of respiratory viruses from patients to healthcare workers during aerosol generating procedures; a continued lack of precision with regards to defining aerosol generating procedures; the safety of cohorting of patients with the same suspected but unconfirmed diagnosis in a common unit or ward with patients infected with the same known pathogen in healthcare settings; the optimal duration of the use of physical interruptions to prevent spread of ARI viruses; use of spatial separation or physical distancing (in healthcare and community settings, respectively) alone versus spatial separation or physical distancing with the use of other added physical interventions coupled with examining discrete distance parameters (e.g. one metre, two metres, or > two metres); the effectiveness of respiratory etiquette (i.e. coughing/sneezing into tissues or a sleeved bent elbow); the effectiveness of triage and early identification of infected individuals with an ARI in both hospital and community settings; the utility of entrance screening to healthcare facilities; use of frequent disinfection techniques appropriate to the setting (high touch surfaces in the environment, gargling with oral disinfectants, and virucidal tissues or clothing) alone or in combination with facial masks and hand hygiene; the use of visors, goggles or other eyewear; the use of ultraviolet light germicidal irradiation for disinfection of air in healthcare and selected community settings; the use of air scrubbers and /or high efficiency particulate absorbing filters and the use of widespread adherence with effective vaccination strategies. There is a clear requirement to conduct large, pragmatic trials to evaluate the best combinations in the community and in healthcare settings with multiple respiratory viruses and in different sociocultural settings. Randomised controlled trials (RCTs) with a pragmatic design, similar to the <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0044>Luby 2005 trial or the <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0280>Bundgaard 2020 trial, should be conducted whenever possible. Similar to what has been observed in pharmaceutical interventions where multiple RCTs were rapidly and successfully completed during the COVID 19 pandemic, proving they can be accomplished, there should be a deliberate emphasis and directed funding opportunities provided to conduct well designed RCTs to address the effectiveness of many of the physical interventions in multiple settings and populations, especially in those most at risk, and in very specific well defined populations with monitoring of the adherence to the interventions. Several specific research gaps deserve expedited attention and may be highlighted within the context of the COVID 19 pandemic. The use of face masks in the community setting represents one of the most pressing needs to address, given the polarised opinions around the world, and the increasing concerns over widespread microplastic pollution from the discarding of masks (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0356>Shen 2021). Both broad based ecological studies, adjusting for confounding and high quality RCTs, may be necessary to determine if there is an independent contribution to their use as a physical intervention, and how they may best be deployed to optimise their contribution. The type of fabric and weave used in the face mask is an equally pressing concern, given that surgical masks with their cotton polypropylene fabric appear to be effective in the healthcare setting, but there are questions about the effectiveness of simple cotton masks. In addition, any masking intervention studies should focus on measuring not only benefits but also adherence, harms, and risk compensation if the latter may lead to a lower protective effect. In addition, although the use of medical/surgical masks versus N95 respirators demonstrates no differences in clinical effectiveness to date, their use needs to be further studied within the context of a well designed RCT in the setting of COVID 19, and with concomitant measurement of harms, which to date have been poorly studied. The recently published Loeb RCT conducted over a prolonged course in the current pandemic has provided the only evidence to date in this area (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0262>Loeb 2022). Physical distancing represents another major research gap which needs to be addressed expediently, especially within the context of the COVID 19 pandemic setting as well as in future epidemic settings. The use of quarantine and screening at entry ports needs to be investigated in well designed, high quality RCTs given the controversies related to airports and travel restrictions which emerged during the COVID 19 pandemic. We found only one RCT investigating quarantine, and no trials of screening at entry ports or physical distancing. Given that these and other physical interventions are some of the primary strategies applied globally in the face of the COVID 19 pandemic, future trials of high quality should be a major global priority to be conducted within the context of this pandemic, as well as in future epidemics with other respiratory viruses of less virulence. The variable quality and small scale of some studies is known from descriptive studies (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0271>Aiello 2002; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0302>Fung 2006; <https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0367>WHO 2006b), and systematic reviews of selected interventions (<https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/references#CD006207-bbs2-0333>Meadows 2004). In summary, more high quality RCTs are needed to evaluate the most effective strategies to implement successful physical interventions in practice, both on a small scale and at a population level. It is very unfortunate that more rigorous planning, effort and funding was not provided during the current COVID 19 pandemic towards high quality RCTs of the basic public health measures. Finally, we emphasise that more attention should be paid to describing and quantifying the harms of the interventions assessed in this review, and their relationship with adherence.