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nopie  1yr ago (vinayprasadmdmph.substack.com)   Edited 1yr ago   3300 thread views

Cochrane review is out and masks have weak evidence that they are not effective

vinayprasadmdmph.substack.com

This one is against rationalists because when Scott wrote his review that masks could be effective many of us trusted it.

I don't blame Scott for failing this one because doing review of hundreds of studies is hard and one person can hardly do it. But this clearly shows that rationalist way of thinking has no special formula, they can be easily mistaken and fall by accepting general consensus just like any other person.

I was impressed when Scott did his review about masks. I trusted it because there was no other clear evidence available. Cochrane hadn't done its review yet and NICE guidelines were silent on the issue. We vaguely knew from previous studies that masks are not effective, The WHO had said so. Suddenly everyone flipped and it was not because the evidence had changed. We simply wanted to believe that masks work and we mocked those who said “no evidence that masks help”.

Even with the belief that masks work, I never wanted mask mandates. I preferred recommendations only, so that no one was penalized or prohibited entry, travel etc if one doesn't want to wear mask. Scott unwillingly had been a catalyst for governments to introduce mask mandates and all this heavy handed approach has been for nothing.

Now we are back to square one, the evidence about masks is weak and it does not support their use even in hospital settings. We can all reflect now what happened in between during these 2 or 3 years. When I realized that Scott's review is clearly insufficient as evidence, I asked some doctors if they have any better evidence that masks work. Instead of getting answer I was told not to be silly, parachutes don't need RCTs and accused me of being covid denier for nor reason. Many so-called experts were making the same mistake as Scott by looking at the issue too emotionally. It is time to get back to reality and admit that it was a mistake and we should have judged the issue with more rational mind.

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Imagine - New large RCT: Emergency medical treatment in rural Nigeria largely ineffective. Okay. But the potential causes are 'long distances so it takes too long to arrive at emergencies, poor training of medical personnel, patients and practitioners hold non-western medical beliefs, lack of resources to purchase good medical technology'. Not 'emergency medicine is bad'.

So, from the meta analysis:

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). .

This is entirely consistent with universal proper use of N95s significantly reducing disese, and surgical/cloth masks not. I'm not sure how to square that with the substack post's comments on N95s, which was "The section on N95 masks was also devastating. [excerpt] Obviously, unlike the types of studies that the CDC likes— hairdresser anecdotes— randomized trials are the best way to separate an intervention from the habits of someone who embraces them."

I wouldn't say the review is good evidence either way on N95s - and the higher quality evidence is more negative than the lower quality evidence - but I don't think the above paragraph is compatible with "devastating". The review notes "relatively low adherence with the interventions during the studies" - it's almost obvious that, for very transmissible diseases, poor adherence to interventions (say, only wearing the mask 75% of the time you're around other people) for a quickly spreading disease might not do much when good adherence would - like, r0 4 -> r0 2, doesn't end up mattering. Of course, that poor adherence is the adherence a general mask nudge / mandate would get, making those particular interventions not useful, but other interventions are possible.

If a random person read the substack, they'd walk away thinking "wow, masks are useless for respiratory diseases". But this isn't the conclusion I come to when reading the abstract - it seems likely surgical masks don't work, and unclear on N95s. Combine that with the 'low adherence', and I continue to believe that 'wearing N95s rigorously probably reduces risk of respiratory illnesses' and 'rigorously wearing N95s may have been a good move during the pandemic if you're old/immunocompromised/etc'. The politics seems to be pushing people away from stuff like that - we're showing how bad the libs are! masks bad mandates bad!

And there's a big difference between 'masks are bad, mandates are bad, this was all a mistake' and 'ineffective implementation of mask mandates was the problem, if N95s were Warp Speeded and given out for free a lot of deaths could be reduced'. The latter is ... arguable, actually - imagine a case where N95s were mandated/heavily encouraged specifically for vulnerable populations (old, immunocompromised, other health conditions), along with early studies making sure they were useful & how to use them effectively, without lockdowns or mask mandates for most.

I don't think that study saying "there is a need for better studies" is biased or misleading, as the substack seems to imply. That's usually true. As the study says, "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", which also seems true. Just because it's a cochrane review doesn't make it perfect or conclusive. It does mean there's a good chance the result useful, but that's different.

Also, I'd be interested in more 'interesting meta-analysis results' posted here - good post imo just because of that, even if it's only posted because of the politics.

From the meta analysis:

Our findings with respect to hand hygiene should be considered generally relevant to all viral respiratory infections, given the diverse populations where transmission of viral respiratory infections occurs. The participants were adults, children and families, and multiple congregation settings including schools, childcare centres, homes, and offices. Most respiratory viruses, including the pandemic SARS‐CoV‐2, are considered to be predominantly spread via respiratory particles of varying size or contact routes, or both (WHO 2020c). Data from studies of SARS‐CoV‐2 contamination of the environment based on the presence of viral ribonucleic acid and infectious virus suggest significant fomite contamination (Lin 2022; Onakpoya 2022b; Ong 2020; Wu 2020). Hand hygiene would be expected to be beneficial in reducing the spread of SARS‐CoV‐2 similar to other beta coronaviruses (SARS‐CoV‐1, Middle East respiratory syndrome (MERS), and human coronaviruses), which are very susceptible to the concentrations of alcohol commonly found in most hand‐sanitiser preparations (Rabenau 2005; WHO 2020c). Support for this effect is the finding that poor hand hygiene, despite the use of full personal protective equipment (PPE), was independently associated with an increased risk of SARS‐CoV‐2 transmission to healthcare workers in a retrospective cohort study in Wuhan, China in both a high‐risk and low‐risk clinical unit for patients infected with COVID‐19 (Ran 2020). The practice of hand hygiene appears to have a consistent effect in all settings, and should be an essential component of other interventions.

... whoa, what? Fomites matter for COVID? I distinctly remember "handwashing for COVID" being something the health authorities recommended early on and were wrong about, and a consensus of 'handwashing doesn't matter, masks do'. Not sure what to do with that paragraph.

Routine long‐term implementation of some of the interventions covered in this review may be problematic, particularly maintaining strict hygiene and barrier routines for long periods of time. This would probably only be feasible in highly motivated environments, such as hospitals. Many of the trial authors commented on the major logistical burdens that barrier routines imposed at the community level. However, the threat of a looming epidemic may provide stimulus for their inception.

Exactly! Again, imagine challenge trials on masks, handwashing very early in the pandemic, with results implemented in nursing homes and hospitals.

Meanwhile in the substack, from the top two comments:

Its that public health officials should never, ever, ever, ever, ever, be given the keys to society again, and that individual liberties need to be fortified against such intrusions in the future because THEY WILL KEEP HAPPENING otherwise. Public health - when it has NO POWER - only has truth. The lies are hand in hand with the power

The follow-on pieces are clear. We need to dismantle, permanently, the current public health apparatus and rebuild it from scratch using some other paradigm. It has been an abject failure in every way. It has shown itself inimical to public health and, short reconstitution, will never be a trusted modality again...and it needs to be.

The first one is weirdly moldbuggian, but ... lol. It's not nearly that bad, and even if it was "LIES. NEVER. FAILURE IN EVERY WAY" is not a useful response.

Combine that with the 'low adherence', and I continue to believe that 'wearing N95s rigorously probably reduces risk of respiratory illnesses' and 'rigorously wearing N95s may have been a good move during the pandemic if you're old/immunocompromised/etc'

The default scientific position is that they do nothing until proven otherwise. You can believe they work if you want, but there is no evidence that they do for something like COVID so it is very much a belief and not an evidence-based claim. Low adherence might be a factor in RCTs, but the majority of people in places like South Korea wear KF94s (with 99.9% of the population masked in public in some form) and they had more cases per capita in the span of two months than the US has had during the entire pandemic.

I don't understand why supposed "rationalists" cling to something with no evidence like this. Why do you think they weren't recommended prior to COVID? Masks are not a new invention. Hell, you could be fined $100,000 for claiming they would protect people from SARS because people knew how irresponsible it was to say that.

Rationalist does not mean 'you must assemble your beliefs from meta-analyses'. Meta-analyses are wrong sometimes.

but the majority of people in places like South Korea wear KF94s (with 99.9% of the population masked in public in some form) and they had more cases per capita in the span of two months than the US has had during the entire pandemic.

99.9% is too high, and anyway if 50% of people weir KF94s in public but not at home, and kf94s are 100% effective, the cloth masks still do not work, so the cloth half instantly gets it and spreads it to the other half. There is also a difference between 'properly wearing n95s significantly reduce your risk of getting an airborne disease' and 'n95s are enough to prevent a pandemic'.

Why do you think they weren't recommended prior to COVID

There was a whole dance about how the mainstream took too long to recognize covid was airborne, and therefore were wrong and stupid.

It should be uncontroversial that Koreans are much much more likely to wear plausibly effective K-94/N-95 masks than Americans though; which being the case means that the fact that COVID was able to spread way faster there than at any point in the US bears significant explaining?

99.9% is probably closer to the truth than 99%. Even in Thailand (where I'm based) for most of the pandemic you saw virtually no one unmasked, even outside. The argument that not enough people wore them does not apply in Asia.

N95s might work if you have it professionally fitted, but given the number of healthcare workers that ended up catching COVID at work I doubt they're that effective either. I think we fundamentally don't understand how COVID spreads.

Our best guess is that COVID is essentially airborne, but being airborne is precisely why masks don't work. The aerosol just leaks out of any gaps between the mask and the face... or with cloth masks, probably directly through the mask itself. If COVID was spread by large droplets, like people coughing or sneezing on each other, then yes masks might have been effective. But given that there's no difference between places that wore them and places that didn't, it's pretty reasonable to say that they are not getting to the root of the problem.

Personally I think it's airborne so easily leaking out of masks, and that it's also infecting people via their eyes as much as their nose/mouth

Even if 99.9% were wearing cloth masks, cloth masks do literally nothing on a population basis!

In Thailand I'd say it's about 60% surgical mask, 40% KF94s or similar. I think Korea's ratio is the other way around

Rationality is actually about understanding the hierarchy of evidence strength. Yes, meta-analyses can be wrong too, but in this case Cochrane report is pretty solid. Even though it is not definitive, it makes no sense to reject it and value some anecdotal cases or even lab based evidence as higher evidence.

Using that logic, do you think handwashing prevents covid? From the review:

SARS‐CoV‐2 [is] considered to be predominantly spread via respiratory particles of varying size or contact routes, or both (WHO 2020c). Data from studies of SARS‐CoV‐2 contamination of the environment based on the presence of viral ribonucleic acid and infectious virus suggest significant fomite contamination (Lin 2022; Onakpoya 2022b; Ong 2020; Wu 2020). Hand hygiene would be expected to be beneficial in reducing the spread of SARS‐CoV‐2 similar to other beta coronaviruses (SARS‐CoV‐1, Middle East respiratory syndrome (MERS), and human coronaviruses), which are very susceptible to the concentrations of alcohol commonly found in most hand‐sanitiser preparations (Rabenau 2005; WHO 2020c). Support for this effect is the finding that poor hand hygiene, despite the use of full personal protective equipment (PPE), was independently associated with an increased risk of SARS‐CoV‐2 transmission to healthcare workers in a retrospective cohort study in Wuhan, China in both a high‐risk and low‐risk clinical unit for patients infected with COVID‐19 (Ran 2020). The practice of hand hygiene appears to have a consistent effect in all settings, and should be an essential component of other interventions.

The general overview states: 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.

Covid as such is basically over now but respiratory illnesses remain. 11% is not much but it is at least something.

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