Researchers will try to measure if some intervention like that works reporting binary PCR positive or negative- but we should want to know what was the severity of the illness. PCR positive with minor illness can be a good outcome indicating that the intervention helped lower the innoculum.
Some of those costs are hard to quantify scientifically or intangible e.g. restrictions on individual freedom, and even the scientifically quantifiable data may have large variability so you have to take an opionated position. Different cultures will obviously take different positions due to different weights they place on risks and values.
Therefore, at this point you leave the realm of science and enter the realm of politics. For whatever reason, people like to pretend it's entirely a scientific discussion but it's not.
I mean discussions are typically both science and politics. Masks lower the amount of people that get sick is scientific fact; why do you think they wear them in the operating room? Whether or not that is "worth" wearing a mask is politics though. However, if you want to convince people of something (aka politics) you may want to appeal to them using logic and for that you'll want to use facts.
Having large variability doesn't make something not a fact. Plenty of males 20-24 do not get in car accidents but that doesn't mean that none of them will or that if you were to insure say 100k males 20-24 and 100k females 20-24 that the males wouldn't in aggregate have higher claims. But given a specific male and specific female its entirely possible that the female gets into an accident first.
This article should be required reading, whatever your views on Covid and other conditions.
Although the attack method of the infection is significant, and the potential victim’s defenses are significant, the raw quantity of infectious agent and the exposure rate are also both important
Nothing is certain. Everything is statistics.
edit: Imagine this being controversial. I didn't realize there were Covid deniers and skeptics here, because what I've stated is completely within established science.
The issue with masks is one side started treating them like a talisman that makes infection impossible, which provoked the other side to say they do nothing.
On a population level, masks are probably close to ineffective against a viral pathogen. You can read the relevant Cochrane review to see that.
On an individual level they obviously do something, but you have to consider other factors as well, such as level/frequency of exposure and the like. Studies from prior to the pandemic suggested that a perfectly fitted N95 mask dramatically reduced flu virus penetration. For a more normally worn N95 the reduction was about 70%. For a surgical mask it was essentially nil. Importantly, a perfectly fitted mask required essentially gluing it to the face of a mannequin.
Final point is, with an intervention whose impact is measurable but imperfect, you have to consider the side effects. I personally know several friends of my teenage kids who now have odd (to me at least) social phobias for which the only “cure” is to wear masks everywhere. Just last weekend I was talking to a friend of my daughter who wears masks everywhere except indoors.
It would be nice to have some numbers to back this up. Let's suppose the "viral load" to acquire a Covid infection is 18 particles, the same as norovirus detailed in the article. And let's say you're exposed to hundreds of thousands of viral particles every minute you spend near a sick person [1]. If a mask reduces your viral load by 50%, is that a worthwhile method of avoiding infection?
Science is an on going process, always open to being overturned.
To the point of masks - I agree with your statement here, but a regular mask (filtered masks should help to some extent) will not protect you from an infected person. An infected person with a mask will reduce the chance of spreading their viral load.
This detail is where I feel people are talking past eachother. Most of covid denial to me seems to be about a psychological reactance to being told to mask up when they are not sick.
One might argue that the extra chance of reduced vectorization is worth mask mandates, but that simplistic purely “scientific” approach is its own problem. You have to argue people where they are at and convince them, not force the “right” view on them and then get upset they are “in denial” or skeptical.
I just don't get the rejection of basic facts.
However there are statistics that areas with more masking had less severe illness. However that’s uncontrolled and some other factors or factors might account for both increased masking and reduced spread. That’s probably the case otherwise the RCTs would show efficacy.
All of the subsequent work is just computer models and doesn’t actually tell us anything empirical. Obviously it’s easier to create a model that produces the desired result than it is an RCT.
Infection is binary or not. You either get exposed to enough to actually result in replication inside your body or you don't. If you get exposed to a small amount and your immune system immediately eliminates it, that's not an infection.
The amount of exposure needed to actually cause an infection is different from person to person depending on their immediate immune response.
But it's not like reducing exposure by 50% reduces disease severity by 50%. Biology doesn't work that way.
^ and the more you have it the less severe it is, until it asymptotically reaches a complete non-issue. As with the common cold.
What I wonder is if we can develop immunity (not boosting, assuming never been infected before) from being exposed to small doses, or do we need at least one full blown infection.
A phrase like "the raw quantity of infectious agent and the exposure rate" is calling attention to the fact that one brief intense exposure vs repeated small exposures over a long time span may have vastly different outcomes despite presenting your immune system with the same number of microbes to deal with.
I guess time is important here - the organism detects the initial virions and prepares defences - so if the infectious dose amount of virions comes after the organism is warned they fail to grow into an infection. But my intuition is that the complexity of that process and path dependence makes that infectious dose so variable - that it does not seem to be any useful.
An analogous process would be human fertilization: it technically only takes 1 sperm to fertilize an egg, but it's millions in order to make the probability of it happening meaningfully high enough.
Of course some viruses are stupidly good at this: it's estimated 5 norovirus particles will trigger a full blown infection.
When you are strong you are resistant. When you are weak you are susceptible. The difference can be huge.
It's a good argument for clean living, regular exercise etc.
What these articles don't talk about are the real-life challenges of concentration and contact time. For example, being a parent with a kid in school they might randomly sneeze or cough in my face while being completely asymptomatic. Then of course we all come down with covid later on.
Secondly, the claims about viral load and shedding have conflicting science on new variants too:
> https://www.nature.com/articles/s41591-022-01816-0#Sec7
i.e
> Nevertheless, in our study, correlation between RNA and infectious VL was equally low between fully vaccinated and unvaccinated Delta-infected patients, indicating that factors other than mucosal neutralizing antibodies may be important for the reduction in infectious VL
> Within 5 DPOS, we found higher RNA VLs but lower infectious VLs in swabs of unvaccinated patients with pre-VOC infections compared to Delta. These results disagree with other studies that analyzed only nucleic acid detection and found 3–10-fold-higher RNA copy number in Delta-infected patients compared to pre-VOC-infected patients
> Although VL is a key element of transmission, the process of human-to-human transmission is complex, and other factors, such as varying recommended protection measures, overall incidence, perceived risks and the context of contacts (household versus community transmission), can influence outcomes in the studies reported.
The best point from this article is the following:
> Transmission dynamics are complex, but the interventions we can take to protect ourselves are comparatively simple.
"Masking, increased ventilation and distancing reduces the number of microbes you’re exposed to. Vaccination increases the infectious dose. "
We really need to move beyond vaccine only, its not working Covid is just too transmissible.
