Masks: How Effective Are They?

4 April 2020. Updated 16 April 2020.

The effectiveness of face masks in preventing transmission of SARS-CoV-2 has been much debated, but there seems to be an emerging consensus that they’re more effective than the authorities believed (or professed to believe) at the beginning of the outbreak. This is important because if masks are a bulwark against infection they could play a critical role in the exit strategy. As a general rule, those developed countries that have imposed less severe social distance measures than the UK are those with a much higher use of masks per capita, like Japan, South Korea and Singapore.

Further Reading

Face masks: much more than you wanted to know‘ by Scott Alexander, Slate Star Codex, March 23rd 2020

Everyone Thinks They’re Right About Masks‘ by Ed Yong, The Atlantic, April 1st 2020

Data suggests masks matter, tests don’t‘ by John Hinderaker, Powerline, April 6th 2020

Face Masks Against COVID-19: An Evidence Review‘, Jeremy Howard et al., preprints.org, April 12th 2020

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Steven Moseley
Steven Moseley
1 month ago

“Trea[t]ing *absence of evidence* as *evidence of absence* is a form of overoptimization.”
https://twitter.com/nntaleb/status/1249289397532602368
“This is the strongest statistical association I’ve seen w/ respect to the virus. Wear a mask, mandate others to wear masks, & remember that @WHO is criminally incompetent. To repeat: @WHO is criminally incompetent.
PS-Don’t get into elevators, buses, etc. unless your mask is N95”
https://twitter.com/nntaleb/status/1249296844712218624
“MASKS One comment about masks and nonlinearities that these imbeciles are not getting. Reducing exposure to viruses by 30% thanks to an “imperfect” mask does not mean reducing risk of contracting the disease by just 30%. By convexity, it must be more than 30%, can even be 95%.”
https://twitter.com/nntaleb/status/1249296844712218624

Gordon Hughes
Gordon Hughes
1 month ago
Reply to  Steven Moseley

Taleb’s basic argument is just an application of elementary probability analysis and is patently correct. The basic arguments against use of masks are three:
(a) there aren’t enough so the public wearing them will detract from availability for more urgent uses [i.e. crass incompetence in supply management];
(b) people don’t wear them properly so the reduction in risk is, say, only 50% rather than 90% [i.e. we don’t understand either probability or the law of large numbers]; and
(c) the best is the enemy of the good or bureaucratic gold-plating that says that nothing should be done unless it conforms to the highest standards [i.e. we need to protect our backs against hindsight even at the cost of bad things happening now].
In many respects the last reason is the most worrying because it has been a prevalent feature of the responses to Covid-19 in many countries and especially in the UK. In any crisis the first action has to be to get rid of most of the deadwood that rises to the top of bureaucracies in calmer times and replace them with people who are both competent and capable of acting effectively.

Steven Moseley
Steven Moseley
1 month ago
Reply to  Gordon Hughes

> (a) there aren’t enough so the public wearing them will
> detract from availability for more urgent uses [i.e. crass incompetence
> in supply management];

The question of effectiveness is orthogonal to whether there is a
paucity of supply. One can make a rudimentary mask at home; local
companies, free from the Government’s strictures around NHS PPE, might
even start making them.

The message “masks are effective yet, while there is a shortage, masks
should be prioritised for health/key workers” is not contradictory, yet
the Government is disingenuous and insists that universal mask wearing
is ineffective among the public.

> [i.e. we need to protect our backs against hindsight even at the cost of
> bad things happening now]. In many respects the last reason is the most
> worrying because it has been a prevalent feature of the responses to
> Covid-19 in many countries and especially in the UK. In any crisis the
> first action has to be to get rid of most of the deadwood that rises to
> the top of bureaucracies in calmer times and replace them with people
> who are both competent and capable of acting effectively.

Indeed. Should this not be the top priority at any time?

Barney McGrew
Barney McGrew
1 month ago

So how would facial recognition work, then?

Richard1
Richard1
24 days ago

An extensive literature review by a former Professor in Canada found that face masks do not provide measurable protection against colds and influenza. https://www.researchgate.net/publication/340570735_Masks_Don't_Work_A_review_of_science_relevant_to_COVID-19_social_policy

Professor Sucharit Bhakdi says face masks for the general population are not needed and may in fact be harmful “germ catchers“.

Richard1
Richard1
18 days ago

Dr. Russell Blaylock’s article: “Face Masks Pose Serious Risks To The Healthy” is summarised: “a recent careful examination of the literature, in which 17 of the best studies were analyzed, concluded that, “ None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”1 [bin-Reza F et al]

When a person is infected with a respiratory virus, they will expel some of the virus with each breath. If they are wearing a mask, especially an N95 mask or other tightly fitting mask, they will be constantly rebreathing the viruses, raising the concentration of the virus in the lungs and the nasal passages. We know that people who have the worst reactions to the coronavirus have the highest concentrations of the virus early on. And this leads to the deadly cytokine storm in a selected number.” https://www.technocracy.news/blaylock-face-masks-pose-serious-risks-to-the-healthy/ https://evidencenotfear.com/tag/medical-experts/

peter
peter
15 days ago

cdc study indicating they do not work: https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article Also, there is no standard at all (as opposed to things like bicycle helmets). This would indicate it’s merely a submission/dehumanization measure, any rag/kerchief/flimsy cloth will do the job.

mikec
mikec
12 days ago

We can see the unfortunate outcome with mask wearing playing out across the NHS and care facilities. People, no matter how hard they try not to, touch the mask during its use and then upon removal fail to conform to good personal hygiene practice. The next time they touch their mouth, nose, eyes they are infected. As a Chartered Safety Professional I’ve spent 30yrs working with people who wear respiratory protective equipment and the sights I see on news bulletins from inside hospital wards scares me sh1tless. The BBC ran a story of a nurse arranging FaceTime calls for patients, I counted him touching his mask 4 times while setting up the call, he then handed the screen to the patient. If they didn’t have Covid before the call they probably have now from touching the contaminated screens. And we wonder why hospitals are now super spreaders?

The worst outcome though will be the infected parties who believe that by wearing the mask they won’t spread the disease, if you trust everybody to be as conscientious as you then you’ve never seen the results of a hand hygiene test in a food factory, Petrie dishes that look like forests due to the bacterial burden caused by incredibly poor personal hygiene practices.

Hopefully NHS staff have been taught how to properly ‘facefit’ their masks as it’s a legal requirement, but it’s rare for training to include personal hygiene issues when using or removing masks. This is borne out by the facts that hospital acquired infections are running a high levels, another cross contamination issue the NHS has failed to get a grip of.

And don’t get me started on NHS staff leaving/turning up to work with uniform on, we don’t let engineers take dirty overalls home so as not to contaminate their loved ones, but nurses can take contaminated uniform home? I’m waiting for the PM to be blamed for that as well.

Stay well, my advice from the current data if you’re over 70yrs only go to hospital if you need A&E/intensive/ICU care.

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