Surgical masks reduce Covid-19 spread, large-scale Stanford study shows • Hacker News Board

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#101

Post by starik36 » Fri, Sep 03, 2021, 6:47 PM UTC

aw1621107 wrote: post #69

starik36 wrote: post #53

So am I understanding the study correctly? > Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were about 11% less likely than those living in control villages to develop COVID-19 The surgical masks are 11% more effective in preventing COVID infection than not wearing masks at all?

Not quite. The wording has to be parsed carefully: > Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were about 11% less likely than those living in control villages to develop COVID-19 So it's not mask vs. maskless; it's promotion of masks vs. no such promotion. The study [0] gives more information: > In villages that received the intervention, mask use inc…

I missed the use of word "promotion". It would be interesting to see the difference in just use of the masks.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#102

Post by mikeInAlaska » Fri, Sep 03, 2021, 6:47 PM UTC

asdff wrote: post #93

majormajor wrote: post #11

Earlier quoted context omitted.

It's surprising to me that cloth masks can't even do the 11% of surgical masks. Which isn't much, but surgical masks are non-optimal for many reasons. Not to mention that this doesn't seem the same as "while wearing a surgical mask you only get 11% increase in protection" but is a population-level thing. There was still non-compliance that presumably lowered the efficacy. I would've intuitively guessed that the bette…

I'm just as surprised. I used to wear a cloth mask and switched to an n95. When I tried the surgical mask I was amazed at how poorly the thing fit along the cheeks and how hard it was to form a tight fit on the nose that wouldn't loosen immediately. Breathing through it offered no resistance at all, in contrast to your typical cloth or n95 that hug all sides of the mask pretty well to your face. I thought this was be…

I have been surprised a few times when wearing a surgical mask looped around my ears, when i had to remove it and then became instantly aware of all the smells of a place I was in. They were definitely isolating me from airborne particles.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#103

Post by mrtksn » Fri, Sep 03, 2021, 6:49 PM UTC

fasteddie31003 wrote: post #77

I was militant pro-mask when I was unvaccinated. Now that I'm vaccinated and have no comorbidities, I'm OK with being exposed to COVID-19. In fact, I want to have a mild case of COVID-19 to get natural immunity. Natural immunity seems to be more effective than the vaccine for long lasting immunity.

Because of disparity between states and the large number of anti-vaxxers, We probably will never reach herd immunity which means that Covid-19 will become endemic and everyone will eventually catch it. With the mutations and winding down immunity it is likely to stay with us.

So, getting a vaccine significantly reduces the risks of death and and getting exposed to the virus naturally will be our immune booster.

That’s why I’m quite relaxed now, I expect to get infected at some point. Maybe not today but in few months when the vaccine induced antibodies can no longer prevent the infection.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#104

Post by kragen » Fri, Sep 03, 2021, 6:49 PM UTC

slg wrote: post #16

majormajor wrote: post #11

Earlier quoted context omitted.

It's surprising to me that cloth masks can't even do the 11% of surgical masks. Which isn't much, but surgical masks are non-optimal for many reasons. Not to mention that this doesn't seem the same as "while wearing a surgical mask you only get 11% increase in protection" but is a population-level thing. There was still non-compliance that presumably lowered the efficacy. I would've intuitively guessed that the bette…

>It's surprising to me that cloth masks can't even do the 11% of surgical masks. Just want to add clarification here. The 11% number is the community impact of the programs designed to increase mask usage. It is not the effectiveness of a mask on an individual level. That number will be much higher since as you said a number of people didn't/don't comply at a societal level.

Given a really effective intervention for a contagious disease, the effectiveness on a community level will be much lower on an individual level. Think about PRC vs. USA: 4636 deaths in PRC, 618591 deaths in USA, even though it's a four times smaller country. There is no measure that even comes close to reducing your risk of death from covid by a factor of 600 on an individual level, but because they were able to get the R number down below 1, they stopped the epidemic.

Normally you would expect effective contagion control measures to have an exponentially larger effect at a societal level than it does at an individual level, even if you don't reach the critical threshold to stop the epidemic: if you can drop R from 2.0 to 1.9, that reduces your individual risk by 5%, but it also reduces the number of cases in the next generation by 5%, the number of cases in the generation after that by 10%, the number of cases in the generation after that by 14%, etc. After 20 generations of transmission you've reduced the number of cases by 64%, which reduces everyone's infection risk by 64%. Of course, with such a high exponential growth rate, that only means that people get infected 1.6 generations later at that point, but if you're comparing different communities at the same time, the difference is about 3:1.

So it seems like probably the effectiveness of the mask on an individual level was truly tiny.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#105

Post by kragen » Fri, Sep 03, 2021, 6:51 PM UTC

dragontamer wrote: post #73

kragen wrote: post #39

Earlier quoted context omitted.

Maybe the relevant point is that it needed to be this big to get a P-value of less than .05, since they only got .04 even with 350,000 people. This is dramatically less effectiveness than I was expecting when I was pushing for mask mandates last year, and within a few months it was obvious that masks alone weren't having the large effect I had hoped for. Now we have quantitative estimates of how small the effect was…

When 70% of people weren't affected by the experiment (13% were wearing masks before the experiment started. 60% of people didn't wear a mask after the experiment), then of course the numbers are going to be small. Seeing a measurable difference when the population only changed from 13% mask to 40%ish mask usage is pretty outstanding IMO.

I don't think that's correct; see https://news.ycombinator.com/item?id=28407881 for the argument in more detail.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#106

Post by Volundr » Fri, Sep 03, 2021, 6:51 PM UTC

theiz wrote: post #68

Quite convinced we have to prepare on getting infected some time. Covid will be around for the coming years and years. Nice that you have less chance of getting that, and then what? You can’t walk around with a mask indefinitely. Saw another report this week that links to the viral load and the impact: low viral load = no symptoms, no immunity. Medium viral load is minimal symptoms, Immunization. High viral load = se…

> You can’t walk around with a mask indefinitely.

I want to be clear I'm not advocating for this, but you can't? Why not? What's the time limit?

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#107

Post by mdp2021 » Fri, Sep 03, 2021, 6:53 PM UTC

rafaelero wrote: post #65

starik36 wrote: post #53

So am I understanding the study correctly? > Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were about 11% less likely than those living in control villages to develop COVID-19 The surgical masks are 11% more effective in preventing COVID infection than not wearing masks at all?

No, you are not interpreting it correctly. The 11% reduction is the effect of the intervention (encouraging people to use masks), which meant that the rate of people complying with the measure went from 12% (control) to 42% (intervention). The 11% refers to the effect of increasing mask use by that magnitude.

So, having roughly one third of the population wear the mask reduced symptomatic infection of roughly a dozen percent. Can one suppose that an almost fully compliant population would see a reduction of symptomatic infections of roughly one third - or am I missing something?

Can this study suggest that a compliant population should see roughly one third less infections?

Edit: for example, the study lasted, I understand, only a couple of months: so, will this timeframe be enough to suppose that the exponential effects can be taken into account, and that the reduction in the infections should be more than just tripled, if one supposed almost full compliance?

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#108

Post by rafaelero » Fri, Sep 03, 2021, 6:53 PM UTC

tomjen3 wrote: post #95

learc83 wrote: post #34

Earlier quoted context omitted.

Libertarians like to make this argument about any government enforcement action. If the government tells you that you can't play loud music after 10pm and you do it anyway, eventually someone will issue you a citation. If you refuse to pay that, eventually you'll get a court summons. If you fail to appear, eventually a police officer may arrest you. If you resist, they will use force to make you comply. It's a bit hy…

It isn't a gotcha, it is just thinking through the second, third, etc order of what you are proposing.

Which it is totally worth it when the counterfactual would be a dumbass playing loud music every night. Is there another solution to this that doesn't require ultimately the use of force?

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#109

Post by Dma54rhs » Fri, Sep 03, 2021, 6:55 PM UTC

nivenkos wrote: post #66

douglasisshiny wrote: post #13

Earlier quoted context omitted.

>However, _mandates_, literally threatening people with police violence, bodily or financial harm, is not the correct way forward. Maybe I'm missing something, but is this actually a thing? Who in the mainstream proposing police violence, bodily or financial harm? The worst I've heard (in the U.S.) is that a business may not allow you to enter if you're not wearing a mask, which is well within their right and reasona…

Have you not heard of the lockdowns here in Europe? In Spain we were forced inside for 2 months, and then forced to wear masks at all times in public - indoors and outdoors. The police got a free pass to beat and arrest people with the excuse of masks or curfew: https://elpais.com/espana/2021-03-28/la-policia-investiga-a-... I got banned from some subreddits just for posting that, because it's become such a political…

I don't think there's a country wearing masks in Europe as much as Spain did (visited many times during the last 1.5 yrs) but it doesn't translate well with infection numbers compared to other EU countries that had lax or non existant rules regarding masks.

Re: Surgical masks reduce Covid-19 spread, large-scale Stanford study shows

#110

Post by hamburgerwah » Fri, Sep 03, 2021, 6:56 PM UTC

cfn wrote: post #14

Here is the paper (or one of them, it is not clear after so many links): https://www.poverty-action.org/sites/default/files/publicati... Bottom line: "The proportion of individuals with COVID-like symptoms was 7.62% (N=13,273) in the intervention arm and 8.62% (N=13,893) in the control arm. Blood samples were collected from N=10,952 consenting, symptomatic individuals. Adjusting for baseline covariates, the 2 interve…

Study is worthless. They did not have the means or funds to properly census the body of people involved, they only took blood samples from consenting symptomatic people and they were highly preselective in choosing the regions they included to achieve the outcome they sought.