Comment by azakai | Hacker News Reader

Comment by azakai | Hacker News Reader

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> We simply don't know if n95 masks provide any protection -- personal or otherwise -- in the real world.

That is simply not true.

First, doctors and researchers consistently say that N95s are known to provide protection against Covid.

Second, this is the first google result on that topic:

https://www.cdc.gov/mmwr/volumes/71/wr/mm7106e1.htm

Quoting from that CDC page:

> What is already known about this topic?

> Face masks or respirators (N95/KN95s) effectively filter virus-sized particles in laboratory settings. The real-world effectiveness of face coverings to prevent acquisition of SARS-CoV-2 infection has not been widely studied.

> What is added by this report?

> Consistent use of a face mask or respirator in indoor public settings was associated with lower odds of a positive SARS-CoV-2 test result (adjusted odds ratio = 0.44). Use of respirators with higher filtration capacity was associated with the most protection, compared with no mask use.

> What are the implications for public health practice?

> In addition to being up to date with recommended COVID-19 vaccinations, consistently wearing a comfortable, well-fitting face mask or respirator in indoor public settings protects against acquisition of SARS-CoV-2 infection; a respirator offers the best protection.

You can say that that might be just correlation, but as those quotes mention, we do know how N95s work: they filter viral particles. That is easy to prove in lab settings. Real-world settings involve more factors, like how well-fitting the mask is, but it would be very surprising if a good N95 properly used did not offer any protection!

N95 masks work. It's a good idea to wear one when relevant.

> That is simply not true.

> First, doctors and researchers consistently say that N95s are known to provide protection against Covid.

I just provided you with the sum total of medical evidence supporting the claim. Citing unspecified "doctors and researchers" is not a rebuttal. You are repeating hearsay, which was exactly my point.

Also, you should know that that MMWR study you've chosen to emphasize here was widely panned by scientists on both sides of the mask debate. It's based on a telephone survey with a 13% response rate. The statistics are hopelessly biased due to the test-seeking behavior of the study participants. It is not credible:

https://vinayprasadmdmph.substack.com/p/mask-studies-reach-a...

It's good that you pointed it out, however, because it's a perfect illustration of the abysmal level of "evidence" that has been used to support similar claims throughout the pandemic. Unfortunately, a many terrible "papers" were published and widely distributed on masks, including many in "good" journals. If you don't understand how to appraise medical evidence, you will be easily misled.

> N95 masks work. It's a good idea to wear one when relevant.

Unfortunately, there is no good evidence supporting this assertion, and "when relevant" is essentially unknown.

It's not unspecified "doctors and researchers". It's the overwheming consensus among medical professionals. The CDC recommends masks, as I linked. So does the WHO,

https://www.who.int/news-room/questions-and-answers/item/cor...

And so does the European CDC,

https://www.ecdc.europa.eu/en/publications-data/using-face-m...

etc. etc. The picture is very clear here.

And, again, the lab evidence is incredibly supportive. We know that N95s filter viral particles. It's possible in theory that that doesn't end up mattering - say if people never wear them right, or if they end up taking more risks because they think they are safer - but that seems unlikely when other evidence says otherwise, and the experts concur.

> The picture is very clear here.

I wish it were.

It should not be difficult to verify that N95 masks filter COVID virus particles effectively.

If such a study had been performed, nobody could reasonably hypothesize that, owing to the properties of the viral envelope, an N95 filter could stop nanometer black carbon particles but not COVID viruses of the same size.

It is baffling that the very basic experiment has not been done: DOES N95 FILTER COVID?

The advancement of human knowledge absolutely depends on VERIFYING assumptions. Institutionalizing common beliefs without empirical data is a crime against science.

Why are you certain such studies have not been done? Plenty of things have been published in that space. For example,

https://academic.oup.com/jid/article/226/2/199/6582941

https://www.frontiersin.org/articles/10.3389/fmed.2021.65431...

You might respond with some specific skepticism about some particular detail in either study. But e.g. the first is in the respected Journal of Infectious Diseases. It passed peer review. And plenty of other studies exist.

The bigger picture here is that every major health agency in the world recommends good masks such as N95s, as mentioned earlier. That is the standard for relevant healthcare workers for good reason. The experts in those agencies have looked at the studies and made that conclusion, which is the general consensus in the healthcare field.

There is some chance all the experts are wrong on this. That happens sometimes. But it's rare.

I gave you a comprehensive review of all literature related to masks, used on people, to prevent actual illness. You don't like the conclusion of that data (there's little clinical evidence supporting their use), but digging up irrelevant laboratory papers doesn't change it.

The first link here is a lab study that doesn't demonstrate anything of relevance to the question: fit-tested masks, in a laboratory, where the outcome is "virus in the air" doesn't tell you if same masks, in the real world will protect against illness in people.

Second link is more of the same: demonstrating that a mask can filter particles, in an ideal setting, does not tell you anything about what actually happens in the real world. For that, you need clinical evidence (which I've already shown you is weak).

Medical science is filled with stories of things that work in theory, but don't work in practice. Literally every drug that failed a clinical trial (i.e. >99% of all drugs tested) worked in the lab. You must do controlled tests on real people to see what really works.

> the first is in the respected Journal of Infectious Diseases. It passed peer review.

Journal of Infectious Diseases is actually not a great journal, and "peer review" is not a magical talisman that prevents publication of bad research. See also: citing the WHO, the CDC, etc., when you've been shown that the evidence for the recommendations they're making is not robust.

> It's the overwheming consensus among medical professionals. The CDC recommends masks, as I linked.

"Consensus", without evidence, is just opinion. Tragically for the credibility of science-based policy, the evidence backing these mask recommendations is incredibly weak. That's just a fact. Repeating to me that "scientists say" something-or-other to be true does not change the fact that the evidence backing the claim is poor.

Medical science is riddled with examples of interventions that "medical professionals" recommended without evidence, only to find that they were ineffective -- or worse, harmful -- when a controlled study was finally performed. Just a few recent examples: hormone replacement therapy; aspirin for heart disease; widespread opioid use for pain; mammograms under age 50. All were "overwhelming consensus". All have been since found to be useless. Some have led to tragic outcomes.

The CDC and the WHO could have run randomized controlled trials to find out of n95 masks are effective at preventing illness. They did not.

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