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The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.

by takeda 5y ago

brobdingnagians 5y ago
That is true; but a large number of people are walking around with cloth masks believing that they are helpful, while that study has shown them to potentially increase risk. It did show "Penetration of cloth masks by particles was almost 97% and medical masks 44%." So that was a positive for medical masks. Though some of the other studies address how those need to be used properly and not re-used. The main point is that, in general, media has not done a good job of transmitting studies on risk reduction; they've mainly done propaganda, which can do more harm by promoting things like cloth masks and not informing people about proper use of medical masks.
- tripletao 5y ago
  The Vietnamese study found that cloth masks increased risk compared to medical masks, not compared to no mask. Confusingly, their control group also wore masks, just in fewer situations: > Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). The first paper doesn't say what kind of mask the control participants wore, but a subsequent paper says only 38/458 control participants wore a cloth mask. I think the implication is that the rest wore medical masks, though neither paper ever says explicitly. https://bmjopen.bmj.com/content/10/9/e042045 https://bmjopen.bmj.com/content/10/9/e042045 That subsequent paper is a subgroup analysis that should be treated with some care, but found comparable performance between medical masks and cloth masks washed in the hospital laundry. That suggests the problem was inadequate hand-washing, not the masks themselves. There is zero evidence that masks increase incidence of disease compared to no mask. RCTs of mask use in public (e.g., DANMASK-19 and earlier flu studies) suggest that the benefit of the mask to the wearer--excluding the benefit of the mask to others nearby from source control--is less than a 50% reduction in disease, with a 95% confidence interval centered somewhere around 20% but including zero. The RCT evidence says nothing beyond that. Public health authorities have indeed spoken with unjustified confidence as to the efficacy of masks. You're doing the same thing here in the opposite direction, though. Given the information above, can you correct your comment?
caddemon 5y ago
That study also focuses on influenza which does not transmit quite the same way as COVID. A bunch of these links were the same thing being shared in the early days of COVID by doctors claiming that masks did not work. Obviously most healthcare organizations have changed their recommendations in light of new evidence specific to this pandemic.
- beagle3 5y ago
  There doesn’t seem to be any evidence specific to this pandemic that masks work. The CDC study released recently puts it at 2% or so. And there was no new evidence in March that caused the reversal from “masks don’t work” to “you must mask up” to “two masks are better”. Obviously there was a reason for them to change their recommendations, but it is not evidence, and might not even be health related - I know someone who was involved with a recommendation in a national organization, and a big part of it was “instilling a feeling of pandemic”.

The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.

by takeda 5y ago

The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.

That is true; but a large number of people are walking around with cloth masks believing that they are helpful, while that study has shown them to potentially increase risk. It did show "Penetration of cloth masks by particles was almost 97% and medical masks 44%." So that was a positive for medical masks. Though some of the other studies address how those need to be used properly and not re-used. The main point is that, in general, media has not done a good job of transmitting studies on risk reduction; they've mainly done propaganda, which can do more harm by promoting things like cloth masks and not informing people about proper use of medical masks.

tripletao 5y ago
The Vietnamese study found that cloth masks increased risk compared to medical masks, not compared to no mask. Confusingly, their control group also wore masks, just in fewer situations: > Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). The first paper doesn't say what kind of mask the control participants wore, but a subsequent paper says only 38/458 control participants wore a cloth mask. I think the implication is that the rest wore medical masks, though neither paper ever says explicitly. https://bmjopen.bmj.com/content/10/9/e042045 https://bmjopen.bmj.com/content/10/9/e042045 That subsequent paper is a subgroup analysis that should be treated with some care, but found comparable performance between medical masks and cloth masks washed in the hospital laundry. That suggests the problem was inadequate hand-washing, not the masks themselves. There is zero evidence that masks increase incidence of disease compared to no mask. RCTs of mask use in public (e.g., DANMASK-19 and earlier flu studies) suggest that the benefit of the mask to the wearer--excluding the benefit of the mask to others nearby from source control--is less than a 50% reduction in disease, with a 95% confidence interval centered somewhere around 20% but including zero. The RCT evidence says nothing beyond that. Public health authorities have indeed spoken with unjustified confidence as to the efficacy of masks. You're doing the same thing here in the opposite direction, though. Given the information above, can you correct your comment?

caddemon 5y ago

That study also focuses on influenza which does not transmit quite the same way as COVID. A bunch of these links were the same thing being shared in the early days of COVID by doctors claiming that masks did not work. Obviously most healthcare organizations have changed their recommendations in light of new evidence specific to this pandemic.

beagle3 5y ago
There doesn’t seem to be any evidence specific to this pandemic that masks work. The CDC study released recently puts it at 2% or so. And there was no new evidence in March that caused the reversal from “masks don’t work” to “you must mask up” to “two masks are better”. Obviously there was a reason for them to change their recommendations, but it is not evidence, and might not even be health related - I know someone who was involved with a recommendation in a national organization, and a big part of it was “instilling a feeling of pandemic”.