How do people resist Covid infections? Hospital workers offer a hint
nature.com
nature.com
I sometimes see articles providing new (perhaps preliminary) info about how effective masks are in different circumstances, how vaccine efficacy changes over time, potential for vaccinated persons to spread the virus, etc. I'd love to see a single website that tracks and reconciles all of those developments into a current summary.
Just for context, my personal use case is trying to estimate the riskiness of having my family participate in various social activities in the next few months.
Great site. Has variables for mask type, vaccine status, etc
I’d add that immunity pretty clearly wanes post infection and vaccination. Especially by six months, but starting at 3.
Single biggest and easiest interventions that people don’t do:
* N95 vs other mask. Well fitted, about as comfortable. Just stupid we’re not using masks rated to filter. Or, a brace on a surgical mask works well too
* meeting outside
* Opening windows. Even a crack helps, if weather calls for AC or heating. People treat this as impossible, but really it just raises electricity costs marginally
* HEPA filter in your home. This is a good idea for other reasons anyway
* Saline rinse in nose when returning home. Again, also not a bad idea for other reasons
There are way too many people out there making "risk models" that are based on assumptions that haven't been validated, and methods that haven't been tested. A model is no better than the assumptions used to create it, and simply because a site tells you what they've done, doesn't mean that what they've done is valid.
We know certain things move the needle and can evaluate their cost. Knowing that is more useful than knowing the specific percent improvement.
Another layer of protection that can be used before a gathering is rapid tests day of (on top of other measures)
And the big idea from the site that risks rise as prevalence rises is true. The site could be off by a factor of ten in absolute terms, but the relative change in risk based on tests + positivity rate will be accurate.
I don't really want to get into this debate, but at least some of what you listed falls under the category of "things people 'know', but which are unsupported by evidence".
Not the best example from the list, but to avoid the ones that are now hopelessly mired in political infighting, "saline rinse in the nose" is almost completely without supporting evidence. Lots of people say things about moistening the mucous membranes and whatnot, but it's basically superstition.
Take this letter, which cites a number of weak/equivocal studies on different viruses, then brings up an actual RCT which showed that a combination gargling / ultrasonic lavage treatment (i.e. not your standard neti pot) within 48 hours of symptom onset (good luck with that), had a ~mediocre effect on symptom duration (-1.9 days) and intra-household transmission (-35%) of unspecified "upper respiratory tract infections".
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7436790/
Based on this evidence, if someone asked me if daily saline rinse made any difference for Covid, the only answer I could possibly give is "we don't know".
But yeah strike that one from the list of interventions we can be 100% confident about.
The rest though are completely certain to help given how aerosols work, so I wouldn’t go too broad with your comment.
You can physically measure both the effect of windows and HEPA on aerosols. With N95 masks they to through specific ratings for filtration of virus sized particles. And going outdoors is like opening a very large window. So physics would have to be wrong for any of those not to be helpful.
Saline in the nose does have well establish physical benefits in the nose. However, the nose’s biology is a complex system so pointing to the physical system is not as simple as measuring a reduction in aerosol particles. But these physical properties were in the back of my kind when I included it in the list. Nonetheless an oversight not to qualify it so thank you:
https://jamanetwork.com/journals/jamaotolaryngology/fullarti...
There's a lot in your comment that is past the available evidence.
Your comment started with the assertion that immunity "pretty clearly wanes post-infection". This isn't clear at all, and in fact, the majority of studies show a robust effect, especially with regard to mortality, but also for simple infection. The minority of studies that show a decline have generally shown minor declines, been extreme outliers, or have focused on meaningless metrics, like "antibody titers":
https://nitter.net/mugecevik/status/1430218372348878860?lang...
Then you talk about "N95 vs. surgical"...there are no studies to support your assertion, outside of pre-pandemic studies of flu in hospitals. Same for the comment about "brace on a surgical mask works well too". Plausible? Sure. Demonstrated amongst a real-world population? No.
Opening windows..."even a crack helps". Well, maybe. Ventilation is certainly more important than masks in general, but what level of ventilation? Is it really true that "even a crack" helps? Not really any data here. Mechanistically plausible, but lots of things are mechanistically plausible and make no difference.
"HEPA filter in your home." Absolutely no evidence of this. Again, mechanistic plausibility isn't the end of the story. There's such a vast array of things called "HEPA filters" that I couldn't begin to tell someone if their particular filter makes any difference at all.
In general, you're leaping from mechanistic theories and/or weak data to strong conclusions. I don't even disagree with most of them in principle, but I wouldn't draw the conclusions you have.
What some of us would have wanted is a frequently updated collection built, as a structure, over the commonsensical questions (e.g. "What is the average risk of transmission in a closed room of this size, this time of exposure and these other variables?"), and filled as studies are published, and annotated with the relevant references ("Virions to get infected: 300 (New Journal of Foo, August 1 etc.)").
The shock sounds shocking: some of us have proposed since forever the question: "how is it possible that people work in high flux supermarkets, where many infected per day must pass, and yet do not either seem to get infected nor to develop antibodies?" However you answer it, the question is urged and present.
Also, marginally, one facetious note (relevant to how tiring these times are... And also relevant to the topic of urging questions): «“I’ve never seen anything like that...” says Shane Crotty, an immunologist at La Jolla Institute for Immunology in California, who was not involved in the research». The last time I have read a similar construction was on Woody Allen.
We __know__ that asymptomatic COVID19 is one of the biggest challenges. Its somewhat a blessing that a large minority of people are so effective at fighting COVID19 that they won't even get symptoms. But without knowing "who" those people are, there's no way to really make a policy decision around their apparent immunity to this disease.
There's also questions about whether or not these asymptomatic people spread the disease. (Much like how vaccinated individuals can stave off the symptoms but still spread it around). Well, I guess that's not a "question" as much as certainty at this point... but understanding the why's and how's would be very useful.
Are you sure?
What if the reduction of viral load, such as social distancing or masks, is what's causing them to have COVID19 resistance?
A cotton mask has 60% filtration. An N95 mask has 95% filtration. If you "breath" in 1000 virus particles, someone with a cotton mask would only breath in 400 of them, while the one with N95 would breath in 50 virus particles.
I have to imagine that viral load would cause some kind of change.
Maybe there is a big difference between breathing in 1000-particles vs breathing in 400-particles. There seems to be no controversy that N95 works (aka: the reduction from 1000 particles down to 50-particles). But cotton masks are still an order-of-magnitude drop (at least, a binary-magnitude).
This is why masks "help", which is their job. Do not be misled by those who argue that less than 100% effectiveness means that masks do not "work".
Do you have a source for this? Because from what little I've been able to find, filtration efficiency for particulate in the aerosolized size range are practically negligible with cotton masks and even surgical masks. Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks, putting such masks in the realm of security theatre.
I suspect studies which show cotton masks having an effect on transmission (in contrast to studies near the start of the pandemic which showed no effect) are failing to consider secondary effects of masking on behavior, namely that masks indirectly remind people of the pandemic and influence their social distancing behavior
Pretend that you're blowing out a candle: make a small "stream" with your lips and blow as far as you can. When I do so, my stream can go at least as far out as my arm, which I think is ~1.5 feet or ~2feet or something (longer than that, because my breath is still "strong" at the full length of my arm in front of me).
Now put a cotton mask on and do the same thing. How far does the stream go? Inches, at best.
Note: oxygen, nitrogen, and CO2 are all much much smaller than mask fibers. But you'll find that these things behave as a __fluid__, and thus we have a fluid-dynamics question rather than one of physical objects hitting a screen door model.
------
The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up.
-----
Or heck, _do_ blow out a candle. This experiment is like, $2. One dollar for a mask, and a second dollar for a birthday candle. Just measure it yourself: the mask grossly affects the distance that oxygen / CO2 / Nitrogen leaves the body.
>The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up.
So instead of breath being directed downward from the nose, the aerosolized particles are redirected upward, where they linger for longer? Moreover, the difference in velocity between speech and "blowing out a candle" makes this a bit of a contrived argument. The key here is that these aerosolized particles have very long settling times - so if they are not being filtered by mask media and instead being blown higher upwards with a mask as opposed to without, then as best masks are useless, at worst they are actually counterproductive.
My counterargument: Nitrogen + Oxygen is even smaller than a virus particle, and the mask seems to redirect N2 + O2 just fine. As such, your mental understanding of how streams flow around people who breath is faulty.
This physics question you're posing is one of fluid dynamics, not one of "bigger" vs "smaller" filters. This simple experiment I show proves that incredibly tiny particles (N2 / O2) behave differently than your mental model suggests.
> Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks
This statement you posted, this right here is wrong. Size has nothing to do with anything when we drop down to sub-microns.
Because exhaling into a mask redirects the fluidlike stream upwards where it lingers for longer. Breathing unmasked directs the stream straight ahead/down.
Here's an example of what I'm describing[0]. Yes, it may be helpful for talking, but otherwise you are potentially increasing the dispersal of particulate when wearing a mask and breathing normally. In this case I am agreeing that filtration is irrelevant.
0. https://nationalfile.com/video-doctor-vapes-through-face-mas...
The fact that you've changed your point is not lost on me. My discussion point was originally levied against your original paragraph:
> Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks, putting such masks in the realm of security theatre.
But sure. I'll play along and pretend that your new "particles act like fluids" statement is what you were saying all along.
> Because exhaling into a mask redirects the fluidlike stream upwards where it lingers for longer. Breathing unmasked directs the stream straight ahead/down.
Then this should be easily demonstrated with a study that shows that masking increases the COVID19 infection rate. Do you have such a study available? (And if you know anything about the mask debate over the past two years, I'm sure you know where I'm going with this)
At a minimum, I've already forced you to admit that cloth masks redirect the flows of COVID19, when originally you claimed that the particles were too small to be effectively filtered.
Ok hold on, I'm not playing bad faith games here. My original claim was that the masks did not filter viral particles. You responded with the birthday candle example, in effect claiming that it didn't matter whether they filtered them, because instead they redirected exhaled air from other people's faces. I then replied to effectively say that this is at best not effective, at worst counterproductive.
I don't believe that in this political climate one would be able to publish a study against the efficacy of masks. I have two studies from the start of the pandemic which showed negligible (≈1-2%) or no benefit to surgical mask wearing, and the fact that even among medical workers there has historically been some degree of dissent as to whether they are indeed effective outside of maybe open surgery.
https://pubs.acs.org/doi/10.1021/acsnano.0c03252
https://med.stanford.edu/news/all-news/2021/09/surgical-mask...
There's plenty of mask studies. The fact that you don't know about them, despite the 1.5 years of mask discussion, is because of your bubble. Not mine.
I've generally seen 60% efficacy from 2-ply cotton designs. The textile study from acs further broke that down into different cottons: tight 600 tpi cotton was more effective than 80tpi loose cotton.
--------
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7263076/
> Published online 2020 May 21.
> In comparison, the 100% cotton t-shirt had a 69% mean filtration efficiency for the 1 μm particles and 51% for the 23 nm particles.
And the big one is the NIH study, conducted relatively early when the mask debate was raging. By May 2020, they already finished their study.
T-Shirt cotton was over 60% effective.
----
Look, its very difficult for me to believe you're arguing in good faith. We're well over a year into this pandemic and you're bringing up talking points I haven't heard in over a year. Your talking points have been completely disproven a year ago.
The screens on my windows don't keep out each and every creeping crawling thing, but it keeps out most. I wouldn't call it trivial either.
The only time "Miasma Theory / Masks" didn't work out was Cholera in the 1800s, because that was from drinking-water instead of an airborne disease (which eventually led to the discovery of microorganisms and modern theories of disease). But there's no denying that COVID19 is airborne. (Sure, we had worries about physical contact in March/April 2020, but today in 2021 we know its airborne).
Otherwise, even the primitive middle-age peasant knew masks / miasma theory was effective to prevent the plague from spreading.
Members of the public posing basic questions. In supermarkets where many thousands per day pass, when the infected are measured as several per thousands, the arithmetic product returns """many several infected per day""" with some contact with the supermarket personnel. Such image creates a difficulty in conceiving a model for transmission, model which people want to form as a basic operation when told "there is an epidemic". The tentative answer "some are probably able to block it earlier than full response" was informally circulating as an answer to the said basic question. ("Informally": when you ask your practitioner, your friend in the lab etc.) This article is a proposal for a formal answer.
> asymptomatic covid19
Covi_D_19 is the Disease. These cases are not cases of diseased - they are much more "at ease" than the asymptomatic diseased. They get their share of virions but block the infection immediately: they do not result as "having been infected" upon test.
You know, like Typhoid Mary?
masses of common people who during their day have some interaction with many infected, yet do not develop the disease, nor show specific antibodies against it.
How is the category you describe even overlapping to them.
One aspect that's worth mentioning imo is that while a percentage of people has been reported not to develop anti-spike antibodies at a measurable level [1], other factors come into play as well.
- Antibody levels after natural infection wane [2] with seroreversion (like seroconversion but the other way around) being common - Some tests used by researchers have low sensitivity (especially many weeks after infection) - Qualitative assays may return negative results even though antibodies may be detected through other methods [3] - There are multiple targets that people may develop antibodies against, testing only for one target like N or S is not conclusive [4, since I can't seem to find a better study on this topic I saw earlier this week]
[1]: https://pubmed.ncbi.nlm.nih.gov/34716320/ [2]: https://www.nature.com/articles/s41598-021-94453-5 [3]: https://pubmed.ncbi.nlm.nih.gov/34213733/ [4]: https://insight.jci.org/articles/view/142386
I was being told with absolute certainty by friends that natural immunity is less effective than the vaccines, while simultaneously a high-N longitudinal study from Israel is showing a rate of reinfection far lower amongst previously infected vs. breakthrough infections in the vaccinated. I think that the certainty of this conclusion is driven by antibody measurements, but not taking into account some of the things this study is mentioning, like memory T-cells.
One of the assumptions that is pretty baked into the public health folks that the scientists are definitely not certain about is the spike protein being the ideal binding target for MRNA vaccines. This article is indicating that they are searching for other targets to create a vaccine that functions, in effect, like what this initial one was SUPPOSED to do: Not be leaky. My suspicion is that the second generation COVID vaccine will be a one and done shot, with no boosters needed. At least I hope so.
"Begging the question" means to presuppose the answer to the question which is being asked while answering it. Eg, "I know God is real because the Bible says so, and since God wrote the bible and doesn't like I know it is true."
What you probably mean is "raises the question."
> The term was translated into English from Latin in the 16th century. The Latin version, petitio principii, "asking for the starting point", can be interpreted in different ways. Petitio (from peto), in the post-classical context in which the phrase arose, means assuming or postulating, but in the older classical sense means petition, request or beseeching. Principii, genitive of principium, means beginning, basis or premise (of an argument). Literally petitio principii means "assuming the premise" or "assuming the original point"
https://en.wikipedia.org/wiki/Begging_the_question#%3A%7E%3A...
> ...the authors examined blood samples collected in the first weeks of the pandemic from nearly 60 UK [hospital] health-care workers ... [who] never tested positive or produced any antibodies to the virus for four months after enrolling in the study. ... In 20 of these ‘seronegative’ participants, T cells had multiplied [together with other markers which] are evidence for ‘abortive infections’
> A far higher proportion of the seronegative participants had T cells that recognize [and disable viral proteins called the replication transcription complex, which helps the virus to reproduce] than did health-care workers who got COVID-19
> Most existing COVID-19 vaccines target SARS-CoV-2’s spike protein ... Spike proteins vary considerably between different coronaviruses. But replication complexes are similar across multiple types of coronavirus, making this part of the virus a promising target for a ‘pan-coronavirus’ vaccine