Cochrane: Physical interventions to interrupt or reduce the spread of respiratory viruses, 2023, Jefferson et al

Physical interventions to interrupt or reduce the spread of respiratory viruses


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.

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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).

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https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/full

 

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.

 

I'm going to stick with N95s, which is all I've used since Day 1 of this, in spite of this. I don't know...is it me? I mean, for all we know no mask does a damned thing. After Omicron came around everyone I know seemed to get it, including myself and my wife, and I doubt anyone is more careful than we are. Not to mention how rarely we go out, having ME and all. Yet that was after 20+ months of being careful & diligent & using N95s only, so it seemed like whatever we were doing in 2020 and 2021 was working. But now, things have changed? Maybe it is pointless after all. I mean, I don't think so, and wouldn't based on what I see in this, which just comes off as weird. At least for the exalted Cochrane, or at least they're supposed to be, unless you know anything about ME and exercise.

But it just seems weird that the Church of the Evidence Base writes that N95s are more or less useless, and anything lesser, equally useless. Maybe everything else we've always heard either was more valid during Delta, or just wasn't quite true to begin with. Cochrane telling us it's basically a waste of time really jumps off the screen at me.

But then who knows what can happen when certain people get together. Maybe putting this out is as much a matter of the authors having some sort of contrarian agenda as anything else. Wouldn't be the first time, right? Even though this wouldn't seem to be the sort of thing you'd expect to see a poor, horribly biased review published on. I mean, this is serious stuff, right?

But one of the author's names jumped out at me, too. It's the next-to-last name, so probably contributed the least, or just wasn't one of the primary figures on this.

Paul Glasziou.

Who just happens to be the Corresponding Author on the Cochrane Review of Exercise as a treatment for CFS. Larun, et al. Which makes him one of the most notable, yet not-often-named, adversaries an ME patient could have. I mean, I don't know, I would think that the galling refusal to take that CFS GET review down would have to be as much his doing as anyone else involved with that, right? As first author, Larun is the name we tend to see primarily; and his name, I'm not sure how much work he's done relative to ME, but...

...just seems, um, interesting that that guy is a co-author on a 'masks don't do much of anything, even N95s' review that I'm not sure people will expect to come from Cochrane.

 

There's no freaking way N95's are ineffective. It's basic physics and engineering; I'm not letting a meta-analysis with potential confounders confuse me. Anecdotally, many people in my social circle have had Covid 2-3 times already, I haven't had it once, and not for lack of going out.

 

Trials of masking in one particular setting (e.g. at a hospital or a school) are always bound to be flawed because, even if the participants perfectly adhere to it, they will remove their masks in other settings where transmission is just as high (e.g. at home with children). This confounding factor is not taken into account.

 

I was trying to be polite. Honestly it seems like a sick joke this is from Cochrane, and that Glasziou is on this might mean nothing yet really begs some strong questions, at the least. @dave30th I am curious if you agree this is a strange, weak review, and is there any possible significance as to his presence, or is that just minor/coincidental/meaningless? I’d be curious what Hilda would say, also.

 

Yes, I think I might wait to hear what a group of trained healthcare professionals says when they're sent to work in a ward of infectious patients without protection because "Pffft, masks don't work anyway".

 

Cochrane continuing to be clown college central. RCTs are completely invalid for this, EBM is a freaking disaster. On the issue of masks they are built on engineering principles using knowledge of physics and unlike medicine, there is no need for evidence-based engineering because everything engineered is based on evidence, medicine is the only profession that has had and continues to use practices devoid of any actual evidence. Actually arguing that better masks don't work better is equivalent to dismissing physics. Physics works, it's predictive, reliable, accurate.

The worst part of this is that you can say exactly the same things about a vaccine-only strategy for COVID, it has low adherence therefore is not viable, but no one cares about reasoning or logic, it's all about what feels right. No one in their right mind would go to a high hazard biolab or breathe toxic fumes wearing only a surgical mask. Because the issue isn't about whether they work, it's about whether they want to tolerate them. Of course they work, it's just that, somehow, medicine has built some weird belief system about the immune system needing to be constantly challenged, or whatever. Many want infections, think they're good. A belief contradicted by evidence.

One thing that's annoying about the whole PPE thing is that's not even about medicine, protection equipment rely on legal standards that apply in many industries. Masks protect workers from toxic fumes in many jobs and there are trillions in economic activity that depend on managing air flow and clean air. This is medicine trespassing on things they know nothing about, about which other people are actual experts about, and decide whatever based on feels, using the absolute least reliable methodologies that literally no else uses because they're unreliable.

 

oh well, i mean that just fills me with confidence!

i will never trust anything cochrane say ever again. I've even now come to the point where i think the reality most likely lies in the opposite of whatever a cochrane review declares.

As @cassava7 says there are loads of confounding factors - not least that most times i see someone wearing an N95 - even Doctors, the nose wire isnt even bent around their nose - there is a massive gap on either side - total waste of time. and they take them off in the room to eat, drink, scratch their noses etc.

They are certainly pointless if you dont wear them correctly & if there is a high viral load in the air anyway it will enter through the eyes, but I'll be wearing them in indoor public places for the foreseeable future, i dont care who sniggers at me. Some of the sniggerers will end up with LC & then they will snigger less.

As @rvallee says, you cant argue with physics, it doesnt need an RCT & an RCT is inappropriate to measure their effectiveness. Those who're being protected from other respiratory dangers in the workplace & have been for yrs can tell you whether they work or not! When worn correctly

 

Oh, you can definitely argue with physics. Just like anyone can argue with a push door by pulling on it with intensely driven motivation. It's winning the argument that's never happening.

 

LOL

YKWIM!

 

So. Why. Put. It. Out. There!?

I’m not even mad anymore. This is too stupid.

They know the evidence isn’t holding up.

And they for sure must know so many people will clinch to this review as ‘evidence’ and deny using masks.

And they must know this will cause people illness, long term disability and for some death.

How on earth does anyone have the conscience to do this?

Of course masks work. Don’t even see the point in making arguments for this.

What was always needed is a good public health campaign teaching people proper fitting and use.

 

Yes, masks reduce the risk of spreading COVID, despite a review saying they don’t

"The question of whether and to what extent face masks work to prevent respiratory infections such as COVID and influenza has split the scientific community for decades.

Although there is strong evidence face masks significantly reduce transmission of such infections both in health-care settings and in the community, some experts do not agree.

An updated Cochrane Review published last week is the latest to suggest face masks don’t work in the community.

However there are problems with the review’s methodology and its underpinning assumptions about transmission."

https://theconversation.com/yes-mas...ovid-despite-a-review-saying-they-dont-198992

 

Sadly I'm seeing anti-maskers on Twitter linking to this thread as evidence for their 'argument'.

 

So it seems from a peek in the rabbit hole that this review is having a huge impact in the antivaccine and pandemic deniers circles. They love it, have a newly-found-but-very-selective love for high-eminence publications.

Same for the recent Lancet paper minimizing Long Covid. The Lancet, and of course Richard Horton, which birthed the modern antivaccine movement. How fitting. Reward failure and you get more failure. Peak evidence-based medicine.

Interpreted evidence can be interpreted many ways. Hence why interpreted evidence should obviously have a lower weight. It's really time for medicine to accept that much of their evidence is of a far lower quality than other scientific disciplines, that they cannot continue to pretend they can assert willy-nilly whatever they want based on this process, whether it's a single study or a large meta review, the overall quality is pretty much the same: low to very low quality.

High quality evidence in EBM is the rare exception. Far from creating a higher standard, it created one where bad evidence is the standard. When you combine that with a coercive and authoritarian model that doesn't respect informed consent, even defaults to gaslighting, no surprise the outcome is disastrous.

 

Moved post

Don’t believe those who claim science proves masks don’t work (Dr Lucky Tran, Guardian)

 

I agree with @rvallee here. Analytical methods (directly measuring particulate filtration) beat empirical methods (in this case, likely with many weaknesses) every time.

 

Love this account and takedowns of this clown study:
https://twitter.com/user/status/1630684414459121665


This engineer has several threads on the topic of evidence-based medicine and how it's not a serious evidentiary process, in fact is probably the least reliable process used by any expert profession ever, with the exception of pre-science medicine. There's some kind of pattern here, having to do with a very insular, almost ecclesiastic, profession.

Fun fact: not a single piece of working technology used by anyone has ever been run through an "evidence-based process" because you pretty much cannot build functioning technology unless everything you do is based in scientific evidence to begin with. And it has to work before it gets out of the lab.

He has another thread on how PPE is not a medical concept but rather legal standards for engineering the equipment. Trying to imagine the thought process of giving untested equipment to firefighters and seeing what works best. What a sick joke. All of this could be so much better.

But instead this, THIS, is basically the best this process can do. I swear it wouldn't be especially hard to publish EBM papers that find that gravity doesn't exist.