Masks and respirators for prevention of respiratory infections: a state of the science review, 2024, Greenhalgh et al

Masks and respirators for prevention of respiratory infections: a state of the science review

Authors: Trisha Greenhalgh, C. Raina MacIntyre, Michael G. Baker, Shovon Bhattacharjee, Abrar A. Chughtai, David Fisman, Mohana Kunasekaran, Joe Vipond et al

https://journals.asm.org/doi/10.1128/cmr.00124-23

"SUMMARY

This narrative review and meta-analysis summarizes a broad evidence base on the benefits—and also the practicalities, disbenefits, harms and personal, sociocultural and environmental impacts—of masks and masking.

Our synthesis of evidence from over 100 published reviews and selected primary studies, including re-analyzing contested meta-analyses of key clinical trials, produced seven key findings.

First, there is strong and consistent evidence for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory pathogens.

Second, masks are, if correctly and consistently worn, effective in reducing transmission of respiratory diseases and show a dose-response effect.

Third, respirators are significantly more effective than medical or cloth masks.

Fourth, mask mandates are, overall, effective in reducing community transmission of respiratory pathogens.

Fifth, masks are important sociocultural symbols; non-adherence to masking is sometimes linked to political and ideological beliefs and to widely circulated mis- or disinformation.

Sixth, while there is much evidence that masks are not generally harmful to the general population, masking may be relatively contraindicated in individuals with certain medical conditions, who may require exemption.

Furthermore, certain groups (notably D/deaf people) are disadvantaged when others are masked.

Finally, there are risks to the environment from single-use masks and respirators.

We propose an agenda for future research, including improved characterization of the situations in which masking should be recommended or mandated; attention to comfort and acceptability; generalized and disability-focused communication support in settings where masks are worn; and development and testing of novel materials and designs for improved filtration, breathability, and environmental impact."

 

Masks work, our comprehensive review has found
https://theconversation.com/masks-work-our-comprehensive-review-has-found-229658

 

Dr Lucky Tran on Instagram:

"A new gold standard review of 100 mask studies finds:

- masks are effective in reducing transmission of respiratory diseases.

- N95 respirators (and equivalent) are significantly more effective than medical or cloth masks.

- mask mandates are effective in reducing community transmission of respiratory pathogens.

The new review showing the effectiveness of masks addresses the flawed Cochrane study, which was deliberately misinterpreted by anti-maskers & some media to spread misinformation around masks.

This new review will serve as a gold standard reference to debunk mask misinformation."

 

For those on Twitter, there are a couple of informative threads too. (Please let me know if you are interested but unable to access, if you want me to copy the text.)

Prof Trisha Greenhalgh:
https://twitter.com/user/status/1793273208654713150


Dr Lucky Tran:
https://twitter.com/user/status/1793301765539979406

 

Masks have served me excellently. Along with sanitizing my hands. I live on my own and only allow family without sniffles in the house. Family live in another city so I don't see them often.

I go out nearly every day catching a train or bus. I wear a surgical mask and a cotton mask over top.

I haven't had Covid yet and I also haven't picked up a cold or flu in over 2 years which is unusual for me. So masks certainly have worked well along with sanitizing my hands when out.

 

It's very debatable whether single use masks do need to be disposed of after a single use. There's plenty of advice (which I haven't got the energy to find now) that drying a respirator that hasn't been used for very long, and leaving it untouched for a number of days, makes it safe to use again. This should be made clearer to the public than it is.

Personally, I handle mine very carefully to avoid damage and dispose of them after about 6 hours of use, and that could amount to quite a lot of separate uses.

But yes, the risk to the environment is a worry.

 

On anti-mask and anti-vax disinformation:

Social media is not the primary driver here, public health and the institutions of medicine are. I see far more people reporting being scoffed at or admonished by MDs about "why are you wearing a mask?" than the opposite. The primary driver of vaccine disinformation, aside from having sprung up out of The Lancet's MMR debacle, is the many lies told about how vaccines would end the pandemic, would eliminate Long Covid and so on. Then the "it's just the flu", then "it's just a cold now", and so much more. It keeps surprising me just how often I see random discussions on Reddit how many people have bad experiences with health care and MDs.

A major driver for anti-masking disinformation has been Cochrane, FFS. The "gold standard" of EBM. Somehow in this paper it's framed as having been misinterpreted, but the authors of the review really did want to push out the disinformation that masks don't work. This review even appears to be in response to it:

And at least there is reasonable criticism of the limits of RCTs, especially when it comes to mechanistic evidence, but the whole "hierarchy of evidence" thing, all of which sits below all scientific forms of evidence used by other professions, is a far broader problem. In truth most of that evidence is so poor that it's too often worse than nothing, because of the asymmetry of bullshit. We saw that with the push to psychologize LC yet again, it's easy to replicate bullshit, while real science rarely happens.

Greenhalgh of course has her own issues with disinformation around Long Covid, most of which evolve around overvaluing RCTs and misinterpreting so-called evidence-based medicine. This criticism applies at least as much to us, although lacking mechanistic evidence from engineering.

Blaming social media while ignoring the far greater role played by medical organizations and MDs is just as irresponsible as, well, disinformation.

And that messaging is largely to blame. It's been a complete mess and there are far too many ideologues pushing for, let's be honest here, a survival of the fittest approach that openly sacrifices people. Denying LC has been the biggest push for the antivaccine movement yet, since all the issues are being blamed on the COVID vaccine. But internal criticism doesn't seem possible in the bubble.

 

I think this sums up the problem with evidence-based medicine as well as anything. Prasad has been pretty much wrong about everything during and since the pandemic, he actually serves as a reliable reverse seer. He has also been pushing awful disinformation, is against any disease control measures, and has been pushing especially harmful disinformation blaming some Long Covid issues, most of which he denies exist, on the COVID vaccine. Oh, and he is a MD, somehow even a professor at UCSF.

He definitely loves the Cochrane "masks don't work" review, which was massively cherry-picked. And there is a case to be made that although the authors of that review meant to promote an anti-masking viewpoint, Greenhalgh in particular, and presumably some of the other authors, has been firmly on the other side. There is biased for and bias against. I really don't like Greenhalgh's stance on chronic illness, and on Long Covid, because of her biases, but on this she is right.

So, really, it all comes down to opinion. Evidence that can't predict anything is basically useless, because it can always be argued one way or another, in the end it's politics. It's all about preferences, biases and egos. We can't agree on what version of reality we experience, even experts about issues that not only do have a knowable answer, but in this case the whole thing is essentially clownish since respiratory protection is not only rooted in physics and engineering, it's widely used in many contexts, including biosafety. For sure if people like Prasad were to go to a lab that handles extremely dangerous pathogens, he would use the protection he pretends doesn't work here.

Because the issue isn't even about whether things like masks work, it's that some people have decided to pursue a mass reinfection policy about this particular virus, and that leads them to dismiss all respiratory protections for all pathogens, since they are fully generic safety devices. It even has led to people not using them while doing things people have long worn respirators, for dust and fine particles, this stuff has consequences.

Basically, this guy is a walking testament to GIGO. But he looks at a study he doesn't like and calls it GIGO. Because ultimately it's not even about what's true, it's about personal preferences. When you want everyone infected, you have to side against any protection. If there is ever in the near future an epidemic with a pathogen this guy considers deadly, he would 100% be masking for his own protection, and likely go right back if it ended quickly.

This is a lot like people like Sharpe who are all about freedom of speech, their speech, despite having spent much of his career oppressing and silencing us. And somehow health and medicine are the only issues where this is happening. There is something deeply emotional, visceral, about it that turns otherwise smart people into fools.