I would answer in the following way. If you are looking for a small effect then an RCT is absolutely essential. If there is a black and white effect, then an RCT is not required. The impact of masking at best is tiny, and at worst it may even have a negative effect.
Now in terms of COVID, even if you don't look at the RCTs, it is evident by just comparing similar countries and similar US states that masking had no impact. e.g. Sweden versus UK, for example or any of the other continental european countries.
Lastly, why do you care about flattening the curve. All that does is prolong the agony because the area under the curve remains unchanged. The only reason to attempt to flatten the curve is if the healthcare system becomes completely overwhelmed. For COVID this was never the case even at the beginning in NYC. Recall NYC never made use of the hospital ship or the Jaffitz center. Yes, things were busy but then hey always are in the winter.
As for the article you linked to, just read it again. they make a lot of assertions for which they have absolutely no evidence. For example, they assume masks work and that this is beyond doubt and "settled science". But it's far from settled, and the RCT data clearly show that masks don't work in the real world. Sure, they may do something under carefully controlled lab conditions, such as speaking into a small hole (e.g. the initial NIH study by Bax & Anfinrud published initially as a letter in the NEJM with a follow-up paper in PNAS), but that's not relevant to real life.
How do you explain that countries who adopted masks early (SE Asia) fared much better with virus control compared to those in the West who didnt? Some would argue that this was like a natural randomized trial of sorts.
My guess is that having an individual as the unit in an RCT on masking during a pandemic is not going to work; you mask well and reach home only to get it from your family; a confounder which cannot be taken care of as it it a pandemic situation. An RCT with the family as the unit, or an RCT on universal masking (as naturally happened in the East vs the West approach), gives the actual answer.
"no compelling evidence that masks did much to halt the spread of respiratory viruses". Ian Miller in multiple places has charts that show masks did little to slow or stop spread and even wrote a book full of those population level charts. Mask do help a little but does that help overcome the disadvantages? Clarity of speech, facial expressions and the minutia of human interaction are lost behind the coverings. Worse is the sense of confidence in protection when the effect is so small. OTOH, a mask does remind us that we must be cautious except when masking is universal, negating even that benefit.
It seems to me that as far as community transmission and general hospital transmission is concerned, the Cochrane Review shows beyond doubt that masking is completely ineffective at a population level. After all, the data show that surgical masks have no impact whether the respiratory tract infection is a virus-confirmed one or not. Likewise for surgical masks vs N95 masks in the general hospital community. One could do as many large cluster controlled RCTs as one likes, and one is going to find the same result. And that's because, the effect, if it exists, is tiny and insignificant in terms of preventing infection or reducing transmission. (And by insignificant I'm not talking about statistical significance but rather the size of the effect is so small it makes no difference whether it is statistically significant or not).
The remaining question is whether masking and what type of masking (surgical vs N95) has any effect in the context of seeing patients with viral respiratory tract infections whether in the ER or an a COVID ward. In other words, the only remaining question is whether there are circumstances where it would be advisable to wear a mask in terms of protection for the individual and whether having the patient wear a mask under such circumstances reduces transmission. And for that narrowly constructed RCTs in hospitals would be required and in addition one would have to distinguish transmission within the hospital from transmission in the community (which can be hard to do unless one is very careful at monitoring, given that nobody words 24/7 365 days a year in the hospital or more specifically in a COVID ward). Anecdotally I suspect the masks may help for short duration hospital visits/examinations (e.g. 5-10 min tops) but after that the masks are useless. And that's from seeing so many people that I know in households who have infected one another despite wearing masks religiously when one member gets sick. But that's just observational.
Flu shots have become de riguer in many parts of the world and questioning their use and utility labels you as an anti-vaxxer in ways similar to the Covid-19 situation.
Can you'll address this issue? If the Cochrane group says that there is no good evidence that flu shots work, then what exactly is going on worldwide? Thanks.
Very well written and clear - thank you! What I love about this one is the description of how a medical study is like a test, it doesn't provide certainty but it updates our priors. What is useful about this is that it allows us to see where the biases are, and, in this case, they're in the 'common sense' section, which pulls current anecdata about mask compliance to state the priors.
And what is clear is Mandrola's priors that "masks don't work" is coming from a place of selective evidence. But this framing is helpful to show that we don't disagree about this study or its conclusions. The bias is in our priors and what we choose to cite for 'common sense.' My "common sense" is the fact that I worked as a hospitalist during the first wave in NYC, wearing only surgical masks for the first week, spending hours in rooms with patients, then n95s until that summer. Mask adherence was high among co-workers. The only healthcare workers I heard of that got sick were those who ate in communal settings in breakrooms. It seems Cochrane's methodology of excluding observational studies is a big mistake here because it seems like those studies should at least inform our priors, even if we take that evidence with a grain of salt.
The challenge with Cochrane reviews, as pointed out by Trish Greenhalgh, is they're insufficient for real world questions and challenges where policymakers may need to make decisions under high uncertainty and may lean toward precaution. Despite my various levels of immunity, in the absence of concrete evidence it seems reasonable to err on the side of caution and wear masks in certain settings. I still do because the risk of harm (to myself or others) is low while the possibility of benefit (to myself and others) seems to outweigh that.
What is worse is that this debate is playing out publicly. I appreciate Mandrola's nuanced take here, and the nuance of the study authors. But the problems arise in the press. Bloomberg, for example, dedicated their health newsletter to the issue this morning, and their takeaway was "masks don't work," framing a looming controversy with how long can Hong Kong's mask policy hold out since masks aren't shown to work?
The nuance, uncertainty and priors are lost in the translation from dissecting the study on its merits to the reporting on it in the press. And, what follows is the propagation of misinformation - overstating the conclusions of a study when even the study authors were quite circumspect and nuanced in how they reported it.
I struggle with this because this is exactly what we should be doing as scientists - debating the science, being transparent about our priors and how much any new study should update those. But channels are getting crossed as we debate this publicly and nuance is lost in translation, making the issue even more political. Which raises the questions, is this the proper place for this debate? Or is it better suited for a medical journal?
I'm still fascinated by the psychology and group dynamics that allowed the entire world to do a complete 180 on masks, to completely abandon the scientific method, seek out the weakest of evidence to support our superstitions we embraced out of nowhere.... it really was like a new Dark Age swept over us in 2020. I'm still in awe by it. There's a certain magic of being able to witness this first hand, as I ignorantly assumed we were "better than that". The superstition phase of medicine, whether it was bloodletting, electroshock, lobotomies, mercury elixirs - all of that quackery could never arise again now that we had "science" and EBM to shield us from such irrationality.
It really is remarkable. I truly hope my grandchildren will think I am bullshitting them when I tell them about 2020 someday.
Great post but the data must be translated to action
Question: You are getting on a plane holding a an n95 mask in your hand wracked with indecision and trying to decide what to do. In deed you have moderate to high uncertainty about the evidence but you must make a behavioral choice. You find your seat and note a big bloke already sitting in the adjoining seat who is slobbering and sneezing into his tee shirt.
{POLLING QUESTION
do you put your n95 on or not ?
YES
NO
PS ( would love to know what Dr Prasad would do? ---[but doubt he is packing n95s)
This post had sizzle. Terse but yet had punch. Lucidly written for those of us without Yale diplomas on the wall or 67-foot yachts down at our local marina. I return now to my bowl of oat cereal with skim milk, some decaf coffee, and the ingestion of daily drugs: angiotensin receptor blockade agent and homeopathic doses of a statin and beta-blocker.
I would answer in the following way. If you are looking for a small effect then an RCT is absolutely essential. If there is a black and white effect, then an RCT is not required. The impact of masking at best is tiny, and at worst it may even have a negative effect.
Now in terms of COVID, even if you don't look at the RCTs, it is evident by just comparing similar countries and similar US states that masking had no impact. e.g. Sweden versus UK, for example or any of the other continental european countries.
Lastly, why do you care about flattening the curve. All that does is prolong the agony because the area under the curve remains unchanged. The only reason to attempt to flatten the curve is if the healthcare system becomes completely overwhelmed. For COVID this was never the case even at the beginning in NYC. Recall NYC never made use of the hospital ship or the Jaffitz center. Yes, things were busy but then hey always are in the winter.
As for the article you linked to, just read it again. they make a lot of assertions for which they have absolutely no evidence. For example, they assume masks work and that this is beyond doubt and "settled science". But it's far from settled, and the RCT data clearly show that masks don't work in the real world. Sure, they may do something under carefully controlled lab conditions, such as speaking into a small hole (e.g. the initial NIH study by Bax & Anfinrud published initially as a letter in the NEJM with a follow-up paper in PNAS), but that's not relevant to real life.
I've followed John's blog and writings for many years. And he is sensible. A small contribution from down under:
https://theconversation.com/yes-masks-reduce-the-risk-of-spreading-covid-despite-a-review-saying-they-dont-198992
How do you explain that countries who adopted masks early (SE Asia) fared much better with virus control compared to those in the West who didnt? Some would argue that this was like a natural randomized trial of sorts.
My guess is that having an individual as the unit in an RCT on masking during a pandemic is not going to work; you mask well and reach home only to get it from your family; a confounder which cannot be taken care of as it it a pandemic situation. An RCT with the family as the unit, or an RCT on universal masking (as naturally happened in the East vs the West approach), gives the actual answer.
"no compelling evidence that masks did much to halt the spread of respiratory viruses". Ian Miller in multiple places has charts that show masks did little to slow or stop spread and even wrote a book full of those population level charts. Mask do help a little but does that help overcome the disadvantages? Clarity of speech, facial expressions and the minutia of human interaction are lost behind the coverings. Worse is the sense of confidence in protection when the effect is so small. OTOH, a mask does remind us that we must be cautious except when masking is universal, negating even that benefit.
It seems to me that as far as community transmission and general hospital transmission is concerned, the Cochrane Review shows beyond doubt that masking is completely ineffective at a population level. After all, the data show that surgical masks have no impact whether the respiratory tract infection is a virus-confirmed one or not. Likewise for surgical masks vs N95 masks in the general hospital community. One could do as many large cluster controlled RCTs as one likes, and one is going to find the same result. And that's because, the effect, if it exists, is tiny and insignificant in terms of preventing infection or reducing transmission. (And by insignificant I'm not talking about statistical significance but rather the size of the effect is so small it makes no difference whether it is statistically significant or not).
The remaining question is whether masking and what type of masking (surgical vs N95) has any effect in the context of seeing patients with viral respiratory tract infections whether in the ER or an a COVID ward. In other words, the only remaining question is whether there are circumstances where it would be advisable to wear a mask in terms of protection for the individual and whether having the patient wear a mask under such circumstances reduces transmission. And for that narrowly constructed RCTs in hospitals would be required and in addition one would have to distinguish transmission within the hospital from transmission in the community (which can be hard to do unless one is very careful at monitoring, given that nobody words 24/7 365 days a year in the hospital or more specifically in a COVID ward). Anecdotally I suspect the masks may help for short duration hospital visits/examinations (e.g. 5-10 min tops) but after that the masks are useless. And that's from seeing so many people that I know in households who have infected one another despite wearing masks religiously when one member gets sick. But that's just observational.
A little tangential, but if we accept Cochrane reviews as a kind of base truth to help with decision making, then what about the Cochrane reviews that question the efficacy of flu shots, both in healthy and elderly adults? https://community.cochrane.org/news/why-have-three-long-running-cochrane-reviews-influenza-vaccines-been-stabilised
Flu shots have become de riguer in many parts of the world and questioning their use and utility labels you as an anti-vaxxer in ways similar to the Covid-19 situation.
Can you'll address this issue? If the Cochrane group says that there is no good evidence that flu shots work, then what exactly is going on worldwide? Thanks.
Very well written and clear - thank you! What I love about this one is the description of how a medical study is like a test, it doesn't provide certainty but it updates our priors. What is useful about this is that it allows us to see where the biases are, and, in this case, they're in the 'common sense' section, which pulls current anecdata about mask compliance to state the priors.
And what is clear is Mandrola's priors that "masks don't work" is coming from a place of selective evidence. But this framing is helpful to show that we don't disagree about this study or its conclusions. The bias is in our priors and what we choose to cite for 'common sense.' My "common sense" is the fact that I worked as a hospitalist during the first wave in NYC, wearing only surgical masks for the first week, spending hours in rooms with patients, then n95s until that summer. Mask adherence was high among co-workers. The only healthcare workers I heard of that got sick were those who ate in communal settings in breakrooms. It seems Cochrane's methodology of excluding observational studies is a big mistake here because it seems like those studies should at least inform our priors, even if we take that evidence with a grain of salt.
The challenge with Cochrane reviews, as pointed out by Trish Greenhalgh, is they're insufficient for real world questions and challenges where policymakers may need to make decisions under high uncertainty and may lean toward precaution. Despite my various levels of immunity, in the absence of concrete evidence it seems reasonable to err on the side of caution and wear masks in certain settings. I still do because the risk of harm (to myself or others) is low while the possibility of benefit (to myself and others) seems to outweigh that.
What is worse is that this debate is playing out publicly. I appreciate Mandrola's nuanced take here, and the nuance of the study authors. But the problems arise in the press. Bloomberg, for example, dedicated their health newsletter to the issue this morning, and their takeaway was "masks don't work," framing a looming controversy with how long can Hong Kong's mask policy hold out since masks aren't shown to work?
The nuance, uncertainty and priors are lost in the translation from dissecting the study on its merits to the reporting on it in the press. And, what follows is the propagation of misinformation - overstating the conclusions of a study when even the study authors were quite circumspect and nuanced in how they reported it.
I struggle with this because this is exactly what we should be doing as scientists - debating the science, being transparent about our priors and how much any new study should update those. But channels are getting crossed as we debate this publicly and nuance is lost in translation, making the issue even more political. Which raises the questions, is this the proper place for this debate? Or is it better suited for a medical journal?
I'm still fascinated by the psychology and group dynamics that allowed the entire world to do a complete 180 on masks, to completely abandon the scientific method, seek out the weakest of evidence to support our superstitions we embraced out of nowhere.... it really was like a new Dark Age swept over us in 2020. I'm still in awe by it. There's a certain magic of being able to witness this first hand, as I ignorantly assumed we were "better than that". The superstition phase of medicine, whether it was bloodletting, electroshock, lobotomies, mercury elixirs - all of that quackery could never arise again now that we had "science" and EBM to shield us from such irrationality.
It really is remarkable. I truly hope my grandchildren will think I am bullshitting them when I tell them about 2020 someday.
Excellent, informative, and succinct post. Thank you.
Great post but the data must be translated to action
Question: You are getting on a plane holding a an n95 mask in your hand wracked with indecision and trying to decide what to do. In deed you have moderate to high uncertainty about the evidence but you must make a behavioral choice. You find your seat and note a big bloke already sitting in the adjoining seat who is slobbering and sneezing into his tee shirt.
{POLLING QUESTION
do you put your n95 on or not ?
YES
NO
PS ( would love to know what Dr Prasad would do? ---[but doubt he is packing n95s)
This post had sizzle. Terse but yet had punch. Lucidly written for those of us without Yale diplomas on the wall or 67-foot yachts down at our local marina. I return now to my bowl of oat cereal with skim milk, some decaf coffee, and the ingestion of daily drugs: angiotensin receptor blockade agent and homeopathic doses of a statin and beta-blocker.