Covid-19: Do many people have pre-existing immunity? | Hacker News Reader

Covid-19: Do many people have pre-existing immunity?

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224 pointsnradov334 comments

Epidemiologist here, a few thoughts reading other comments:

-Death data is preferable to new cases in some ways, since it doesn't rely on testing, which ramps up/down from locality to locality and over time.

-To compare deaths from the Spring with deaths recently isn't apples to apples: we know now remdesivir and dexamethasone are helpful treatments, especially the latter, and these may help reduce mortality rate.

-Mortality now may be lower partly due to: if the virus killed off the more vulnerable populations (nursing home) early on, it has less frail individuals to infect now. These communities got ravaged, we had something like 40% of deaths in my area in nursing homes in our 6-week case peak.

-Trying to tease out immunity is very tough as well, early on there were few good tests and their specificity and sensitivity were less well known. At my agency, there were multiple tests we were collating, with different false positive and negative %s, and different reporting times (which all can influence R0, the variable number our behavioral interventions seek to tamp down).

-Comparing different countries is very tricky. Sweden is a favorite example for non-lockdown approach, but there we see it's very tricky to tease out the benefits. On the one hand, they didn't do much better epidemiologically than their neighbors. On the other hand, their economy was surrounded by locked down ones, so that may have tamped down any benefits their non-lockdown would've garnered due to neighbors' activities. Did it pay off? The verdict is still out, IMO.

Things are very complex in infectious diseases epidemiology. It's extremely hard to know anything for certain with this virus, it's behavioral tangled up with comorbidity with genetics and demographics and evolving treatment and viral dosage and strain of virus...it will take a few years of unpacking the mountains of data before we truly have a grasp of what happened here.

q for you: early on, there was a big variance (region vs region, one region over time, etc) in how mortality was reported, e.g. heart attack vs COVID, single cause vs multi-cause, etc. Is mortality more standardized now?

I've been wondering this myself; last I heard (2 months ago, fairly credible investigative journalism), there was a massive disconnect, state to state, how COVID-19 deaths were assessed and recorded. IIRC, Florida was on one end of the spectrum, tagging deaths as from any comorbidity present (only tagging as COVID if they couldn't find anything else), to California, which was tagging as COVID without test confirmation, if enough of the symptoms were present.

California and Florida have about the same gap between excess mortality and registered covid deaths, with Florida being slightly better.

You can see it here:

https://www.nytimes.com/interactive/2020/05/05/us/coronaviru...

Do you have any links/sources for this?

I think the CDC numbers say that, at least nationwide, 6% of deaths list only Cov 19 as the cause of death. 94% list other causes. This data is so messy, I don't think there is much of a take away. Of the 6%, could there have been other reasons which were missed? Certainly some. Of the 94%, would they have died anyway sans Cov 19? Certainly not all, and not then.

As others have pointed out, we should pay attention to the delta in deaths over some other year with an average flu season, and a year with a bad flu season. Someone will run these numbers at the end of 2020, I hope, and then we'll have a better idea of the effect of this particular pandemic.

They've already been running those numbers and they're available on CDC's website: https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm (Scroll way down for the chart)

We had a bad 4-6 weeks a couple months ago but we're already down in the range of a normal flu season as far as deaths go.

I'm pretty sure 6% was deaths where "only" covid was listed.

In most cases, doctors are more specific. So they may put covid & pneumonia. Pneumonia being any infection of the lower respiratory system. Which would in almost all cases, be caused by covid unless they also had a separate infection.

Doctors will also often list complicating factors like obesity (45% of Americans are clinically obese).

This is actually right along with the confusion of the public and media for the official coroner's report. The coroner listed cardiopulmonary arrest as the cause of death "complicated by" (in other words "brought on by") someone pinning him to the ground and blocking his airway. Drugs in his system and prior health conditions were listed in the report as any thorough coroner's report should. But they were not listed as complicating factors for his death.

Cardiopulmonary arrest is -not- a heart attack. (that's a myocardial infarction). It means your heart stopped pumping and your lungs stopped functioning. Which is how most people die.

Not GP. In my opinion, the only reliable measure is excess death (if you believe death count, which I trust for most countries, but not all countries), because it is invariant to these (often political) classifications. See e.g.[0] (it is up-to-date for 11-sep, despite the link date saying April 21). In fact, these graphs would look the same even if you didn't have access to any testing/diagnostics/causes-of-death.

It is easily visible which countries have gone back to baseline, which countries haven't, and which didn't even have a "first wave", which likely means that they are in great danger of one happening.

[0] https://www.nytimes.com/interactive/2020/04/21/world/coronav...

Would't any preexisting immunity be accounted for by any decent estimate for R0 and the IFR?

Not really. If there is existing immunity then the measured R0 will be lower than the actual R0, but we don't know how to measure the true R0 in absence of the current population with their immunity so we can never know what the true R0 might actually be.

Note that true R0 is a concept I made up on the spot. I think it is clear what I mean but experts in this may have better terms.

A first-order SIR model with unmodeled pre-existing immunity will be accurate initially, but get gradually more wrong with time. For a simplified, non-representative example with fake numbers, let's say half the population already had perfect sterilizing (they don't get sick, and the virus doesn't replicate at all so they can't spread it to anyone else) immunity. Then an apparent R0 of 2.5 would imply an actual R0 of 5. But R0 = 2.5 would imply you need 1 - 1/2.5 = 60% of the population infected for herd immunity, while in that hypothetical case you'd need only 30% infected (so the 50% initially immune plus that 30% make 1 - 1/5 = 80%).

The above still assumes a well-mixed population, but with heterogeneous susceptibility (using the terminology from [1]). There's also heterogeneous connectivity (i.e., the fact that some people have more social contacts than others), which further reduces the herd immunity threshold.

To be clear, the above is a fake example. We know that almost no one has perfect pre-existing sterilizing immunity to the novel coronavirus, because we've seen highly-connected populations (homeless shelters, slums, boats, etc.) where almost everyone tested positive. But that doesn't mean everyone is equally susceptible! Immunity is a continuum, not a binary thing, and the 20-50%[2] of people with reactive T cells very likely get less sick given the same initial viral dose (or, stated in the other direction, would need a greater viral dose to get equally sick). They also might spread the virus less, though that's more speculative.

Finally, I'll note that the herd immunity threshold is the point where R becomes < 1, and the number of people currently infected starts to shrink instead of growing. People still get infected on the downslope, so the fraction of people infected can overshoot higher (and potentially much higher, especially if no precautions are taken to slow the spread).

1. https://www.medrxiv.org/content/10.1101/2020.07.23.20160762v...

2. https://science.sciencemag.org/content/early/2020/08/04/scie...

> We know that almost no one has perfect pre-existing sterilizing immunity to the novel coronavirus, because we've seen highly-connected populations (homeless shelters, slums, boats, etc.) where almost everyone tested positive.

We don't actually know that. Even if some significant % of the population has pre-existing sterilizing immunity, then by chance we'd still expect to have many groups of people where everyone is vulnerable.

Fair point. I still think pre-existing sterilizing immunity is unlikely, since (to my non-biologist's understanding) antibodies tend to be specific, and T cell immunity is broader but not usually sterilizing. The existence of those unlucky groups isn't conclusive evidence in itself, though, especially if pre-existing immunity is distributed non-uniformly (which it probably is, if there's some genetic basis, or if different strains of common cold coronavirus swept through different regions last year and primed people's T cells differently).

Of course non-sterilizing immunity could still be incredibly valuable. They're speculating that the current vaccine candidates may not cause sterilizing immunity[1], but immunity that turns a fatal illness into a bad cold (or a bad cold into a couple of sniffles) is great, whether naturally pre-existing or from a vaccine.

1. https://www.statnews.com/2020/05/22/the-world-needs-covid-19...

Well, its a bit unfair to say that since Sweden didn't reap all of the benefits of protecting their economy, because of neighboring countries' following a different path, that something was wrong with Sweden's approach.

If I had the right idea, but am surrounded by people with the opposite idea, that doesn't mean my idea became wrong. It only means I maybe wasn't the best at convincing my neighbors.

Where did they say something was wrong with Sweden's approach?

Because you exist within a system whether you like it or not, so the optimal/correct solution must account for those variables, including your ability to entice cooperation. So yes, you would still be wrong, just not for the narrow way you’re choosing to redefine “correct.”

Any thoughts on Sweden (and many other EU countries) saying masks have very little scientific evidence for the little benefit they supposedly offer. How can scientists in different countries have so different views. Some countries preach masks like holy water and they both say God (science) is on their side.

Where would I look of I wanted to follow geographicly diverse epidemiology news / publications / groups / individuals, not just covid related.

Thanks in advance.

Comparing Sweden with its neighbours really highlights how poorly it has done: https://ig.ft.com/coronavirus-chart/?areas=fin&areas=swe&are...

Pretty much any way you slice the data, a lot more people died in Sweden than in its neighbours.

You can see the same pattern in excess all cause mortality too: Denmark 200, Finland 600, Norway 0, Iceland 0, Sweden 5500.

Now Sweden has a population slightly less than Finland and Norway combined, and figures can be difficult to compare, but still it's hard to avoid the conclusion that so far, around 4000 people in Sweden have died because of differences in policy compared to its neighbours.

The least you can say is that Sweden didn't manage to test as many as its neighbors did. It is claimed the influx of infected was greater etc, but lack of tests meant that it was hard to get it under control too.

The better question that Sweden may help answer is whether shutting down the economy was worth it. Was the deaths of 5,500 people worth keeping the economy open, in other words, could you have saved more lives by pursuing other health priorities and let covid run it's courses as Sweden elected to do?

This. The deaths directly attributed to the virus alone aren't the only relevant deaths. Suicides are up. Domestic violence is up. Child abuse may be up but schools are all "virtual" so good luck detecting it (as if it wasn't hard enough when kids were mostly in school).

Talk about throwing out the baby with the bath water...

Could you show any data that supports your assertion about rates of suicides, domestic violence, and child abuse?

in NZ suicides were down over the lockdown period.

NZ is an outlier in a lot of ways, to include population size and distance. The also cracked down on firearms ownership recently, too -- #1 choice for suicidal men.

huh. Thats such a weird place to go.

It was only the automatic weapons, Im pretty sure any suicidal men could probably still hit themselves in the head with a single shot from a distance of 0.2 feet...

I don't at all doubt that lockdown has had a number of second order problems (and benefits too), but the the figures I quoted at the end were excess all cause mortality, so those are all already included. And indeed, many countries with net 0 excess all cause mortality certainly had corona virus deaths, but lockdown and related benefits appear to have saved more people than the virus killed in those countries.

I think most people who are worried about secondary effects from lockdowns don't think that these will be visible immediately during the pandemic. But rather as a higher baseline of mortality in the coming years. This is just my guess. I'm not an epidemiologist, so I have no real expertise in how these effects usually manifest themselves in the statistics.

I didn't consider those second order effects. When I wrote my comment, I had in mind only the dollar cost of averting the disaster. When we spend whatever trillions of dollars shutting the economy down and limiting output, we necessarily take from other priorities, like strengthening emissions controls, or making cars safer, or re-wilding spaces, or spending money on providing people with affordable preventative medicine that could extend the duration of life.

Actually the figures I gave at the end there were excess all cause mortality, not coronavirus deaths. So far, they have definitely not saved more lives.

Just for some perspective: during the 2017/18 season 2822 people died from the flu in Denmark. https://www.ssi.dk/aktuelt/nyheder/2020/influenzasasonen-201...

Sweden had a high initial death rate but now their average daily deaths have been near 1 for several weeks. So whatever they're doing lately seems to be working well.

https://www.worldometers.info/coronavirus/country/sweden/

Look at the charts I shared, they took about an extra 120 days to get the death rates down to the same level as their neighbours. Now, it's not exactly comparable since they have a larger population, but even the average daily deaths of 1 is not an indication that they're doing well compared to the other nordics.

Playing devil's advocate:

The death counts are what they are, but on the other hand, Sweden is extremely unlikely to experience a 2nd/3rd wave, which is experienced now by the countries you listed - it's not even halftime yet fighting the virus, it's too early to say who did better.

The "any way you slice the data" is not so clear either. As someone pointed out, Sweden had fewer deaths (in the thousands!) in previous flu seasons, I've read the hypothesis put forward that part of the reason Denmark has done so much better is that their weakest already succumbed to the flu in 2017/2018, whereas Sweden's were spared. Nearly impossible to prove or disprove, but there ARE ways to slice the data that make the attribution to policy less convincing.

> Now Sweden has a population slightly less than Finland and Norway combined, and figures can be difficult to compare, but still it's hard to avoid the conclusion that so far, around 4000 people in Sweden have died because of differences in policy compared to its neighbours.

Another way to slice the data that is important: Sweden has, by far, more black skinned immigrants than Norway (and I think Finland too) -- which are faring worth everywhere, likely some sort of sunlight/vit-D related process. A significant number of those who died in Sweden are immigrants.

If you compare Sweden to Belgium (which had strict lockdown, but similar immigration patterns), the policy argument is less convincing again.

I find the flu argument pretty weak, but it ultimately boils down to a claim of demographic differences (that Sweden had more people at the beginning of the pandemic that were likely to die than neighbouring countries).

Belgium feels like a cherry picked example, having as it does a miserably poor record compared to its own neighbours, and being rather unlike the nordic countries in lots of other likely relevant ways - climate, population density, etc.

Perhaps a more likely demographic cause might be the age of the population in Sweden, which I believe does have a particularly old population.

The racial/skin colour angle is difficult to evaluate. There may be something to it, but there are so many potentially confounding factors - immigrant populations are unlike the native population in a number of ways. Some of the ways they are different are that they are overrepresented in high risk groups like front line medical workers or living in poorer quality accommodation or having more difficulty getting access to health care. If the primary cause that they are overrepresented in covid-19 deaths relates to any of those, then having a lower immigrant population may just redistribute the deaths rather than reduce them (the bottom socioeconomic 10% will likely be overrepresented in deaths, and that bottom 10% may feature more or fewer immigrants).

My point is that it’s not as clear cut as “any way you slice the data”.

Sweden’s immigrant population is not remotely like the US one. They are NOT over represented in healthcare work, AFAIK they are underrepresented (to a fault, of having almost no representation). They do live in lower quality housing, on average, but have access to nominally equivalent medical services (Sweden has socialized everything; once you are “in the system” you are entitled to everything, though rich people can buy some extras)

Also, It’s a little disingenuous to say “Belgium is cherry picked” without extending a similar courtesy to Sweden.

All in all, it’s too early to call winners and losers, and there are many ways to slice the data that don’t make Sweden look bad at all.

The ship epidemics give an indication of whether this is the case. The USS Teddy Roosevelt had an epidemic and everyone onboard was tested. 20% tested positive for the virus. 60% showed antibodies.

Arctic cruise ship after 21 days: "Of the 217 passengers and crew who remained on the ship for the entirety of the voyage, 128 tested positive for the coronavirus, the researchers said. They added that of those who tested positive, 24 exhibited symptoms and 104, or 81%, did not."[2]

There are many other ship epidemics, but those are ones that had 100% testing. That puts a ceiling on pre-existing immunity at somewhere around 40%. No floor from that data.

[1] https://www.cnn.com/2020/06/09/health/covid-19-investigation...

[2] https://www.cnbc.com/2020/05/27/over-80percent-of-coronaviru...

> That puts a ceiling on pre-existing immunity at somewhere around 40%.

Only if pre-existing immunity and sailors/passengers are evenly distributed.

COVID tests/PCR tests only test whether a person is actively infected. They look for viral RNA present in your system. Therefor, if you recover (10-14 days after infection, ~7 days after symptoms) then you will not test positive for COVID.

https://www.medicaldevice-network.com/features/types-of-covi...

That is not correct. The PCR tests are highly sensitive and continue to show positive results from remaining dead virus particles for some patients weeks after the infection has been cleared.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237903/

The point is the OP's math assumed that everyone (ALL) who recovered from COVID-19 would test positive. What you're saying is that SOME people who have recovered could test positive.

Pre existing immunity may not preclude testing positive?

Not an expert here but could preexisting immunity just mean the virus has trouble really taking hold and wreaking havoc before it is shut down, as opposed to never being infected at all?

I guess what I’m asking is whether immunity is truly binary.

It does. To test positive viral load needs to be at a certain level, that can only happens if cells are infected and producing virus particles. If that's happening you're not immune.

Current US PCR tests are set to be so sensitive that they can detect a single copy of viral RNA. This has been an under-reported fact that should be more widely known:

https://www.nytimes.com/2020/08/29/health/coronavirus-testin...

Immunity is indeed not binary. There's sterilizing vs non-sterilizing immunity, for instance, sterilizing immunity meaning that the pathogen is purged before infecting cells (emphasis mine):

> Without a strong mucosal response, injected vaccines may be less likely to produce so-called sterilizing immunity, a phenomenon in which a pathogen is purged from the body before it’s able to infect cells, Dr. Durbin said. Vaccinated people might be protected from severe disease, but could still be infected, experience mild symptoms and occasionally pass small quantities of the germ onto others.

https://www.nytimes.com/2020/07/14/health/coronavirus-nasal-...

The research says that some people may have T-cells which promote a more robust response to the virus, if their antibodies don't succeed.

From the article below "This means that infected people who did not develop symptoms or antibodies may still be immune to Covid-19 via T-cells memory"

It does a good job of explaining the difference between immunity acquired by antibodies vs T-cells.

https://medium.com/microbial-instincts/if-antibodies-fall-sh...

"That puts a ceiling on pre-existing immunity at somewhere around 40%."

No, you're assuming that pre-existing immunity excludes people testing positive for the virus. You can test positive while mounting a robust immune response. In fact given that most infections are minimally symptomatic, it's arguable that immunity is the norm, not the exception.

That isn't what the word immunity means.

I'm not sure what you're trying to argue, but an immune response in no way precludes testing positive for a virus.

Particularly at the testing thresholds we are using in the US, where as little as a single copy of the virus RNA can be detected, a great number of people test positive for weeks after their immune system has defeated the virus.

He may not be wrong.

T-cells are not like antibodies, which is the immunity you are thinking of.

What the words means in common usage doesn't have to track what immunity actually is. Colloquially, immunity means sterilizing immunity. Actually, immunity doesn't have to be sterilizing.

You shouldn't be downvoted. Immunity is a spectrum, not a binary condition. If the pre-existing immunity hypothesis is correct then it probably doesn't provide complete protection in all cases. It might cause some patient to experience asymptomatic or paucisymptomatic infections instead of full blown clinical COVID-19. Those patients can still test positive.

The CDC estimates that 40% of infections are asymptomatic.

https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scena...

Yes, this is exactly correct. And there's some reason to believe that the most severe cases are the result of an overactive immune response (though I haven't kept up with research into this hypothesis, so don't take my word for it).

I don't tend to place a lot of emphasis on downvotes on this topic. I have a background in this area, so I know when I'm on solid ground, and there are a lot of people who simply don't want to accept the prevalence of asymptomatic infection, even today.

More generally, nuanced opinions about this virus are targets for attack from both sides of the political spectrum. It's a tough time to be a scientist.

Many of the ship epidemic stats counted pre-symptomatic people as asymptomatic.

This is assuming antibody tests are accurate.

Antibodies decline drastically after 2 weeks and the T cells and other immune systems take over.

So, the question is how accurate are the antibody tests for Covid-19?

> They added that of those who tested positive, 24 exhibited symptoms and 104, or 81%, did not

Does that distinguish pre-symptomatic from true-asymptomatic? 100% testing is not enough without follow up testing for a while.

Flipping a coin 10 times and seeing that there are 7 heads does not imply that the probability of tails has a ceiling of 30%.

This is another really great reason why the herd immunity threshold is lower than it has naively been claimed. If the effect is as large as TFA says then the threshold is actually much lower than the ~60% level.

This has a big impact on the estimated death rate for achieving herd immunity. The other factor in that estimate is the CFR which is also plummeting over the summer, although there’s reason to believe CFR could go back up somewhat in the winter depending on how much the gain was environment versus how much is due to better treatment protocols and therapeutics.

For example, if the immunity threshold goes from 60% -> 20% and the CFR goes from 5% -> 1% the estimate death toll is reduced to 1/15th (6.6%) of the original estimates.

Not really, "immune" people can still contract and transmit the virus.

So the effect of T-Cell immunity is already accounted for in R0 and IFR estimates.

> This is another really great reason why the herd immunity threshold is lower than it has naively been claimed.

It sounds like you're starting from the happy assumption - herd immunity is much easier to achieve than we believe - and working backward to find data which justify your hope. To get good predictions, we have to be dispassionate and not assume the happy case.

A realistic assessment would probably assign some sort of a probability range to different thresholds - a model might suggest there's a 60% chance the threshold is 60%, a 5% chance it is 40%, a 20% chance it is 80%, a 10% chance it is 90%.

And any model has to take into account that any piece of data might be wrong, including this data about T-cell immunity.

In my area, as in Sweden, cases have been declining for many weeks now. Lockdown didn't become stricter. People didn't become more compliant; rather the opposite. Why aren't cases skyrocketing the way they were a couple of months ago? What explanation is there other than the herd immunity thresholds being wrong?

Mask compliance is reducing spread?

Sweden has recommended against wearing masks. So mask "compliance" would mean not wearing one, which should have led to an explosion of cases, no?

I’d say there has just not been a recommendation or mandate to wear them. There hasn’t been a recommendation against them. It could still happen they say, at least regionally e.g in public transport in one region for example.

A recent survey found only 6% mask compliance in Sweden so that's probably not a significant factor. There must be something else going on.

https://www.telegraph.co.uk/travel/destinations/europe/swede...

Did they open schools there as well? Those increases seem to be around early September, around when in many countries with those enormous increases have opened their schools. Could it be this a significant factor?

Yes, and schools were never fully closed.

I don't think our mask compliance has increased since the earlier spike; I would say the opposite. I don't have any hard data of course, so it's possible. I hope someone is collecting this data.

If masks are truly effective enough to alone cause the dramatic change we're seeing, then the initial advice that they weren't necessary was utterly disastrous.

I see one mask maybe every other day (major city in Sweden). I would guess mask usage is close to zero.

For my data point I’d say around 1-5 of 100 in large grocery stores (Stockholm). Outside almost no one.

It is tempting to see masks as a solution, but I doubt they are. We had quite strict mask requirements (bordering absurd, like wear the mask in the woods, being alone), and they are again required in indoor public places. Our neighbours in Latvia never required masks and hardly anyone wears them. They have just a fraction of new cases we have.

Data so far seems to suggest the opposite. Countries with harder enforcement of face masks seems to have had larger outbreaks later.

There has been earlier WHO studies that suggests improper use of masks may be detrimental, but it might just as well be confounding effects of something else.

Really? Germany, Taiwan and Korea disagree.

Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and now is having a severe outbreak again[2]. What explanation is there other than herd immunity not having been reached?

As for Sweden, there's a lot of variety in human behavior and a lot we don't understand about the virus, and there are many possible explanations for the lack of major spread in any particular area. Sweden has continued to post a steady low level of cases over the last two months, not a continuing bell-curve decline, suggesting the virus is still consistently finding new hosts, just at a low and steady pace.

[0] https://www.reuters.com/article/us-health-coronavirus-spain-...

[1] https://www.theguardian.com/world/2020/may/21/just-7-per-cen...

[2] https://medicalxpress.com/news/2020-09-doctors-hard-hit-madr...

The number you're citing for Stockholm is from April, well before the outbreak became severe in Sweden. Cases in Sweden continued to grow after that, and didn't peak until late June, when daily case counts were 3x higher than in April. (Although it's important to point out differences in testing - the positivity rate peaked April 20th - 26th).

That's a different experience than Madrid, where the virus hit much earlier. By the end of April, daily case counts were 1/5th of their peak in Madrid.

I'm not aware of a more recent study.

The simplest explanation for Madrid is that it locked down too early, and herd immunity (which seems to occur at about 20-25%, based on Antibody testing of New York and Sweden) was never reached.

Lockdown also seems to increase the threshold for herd immunity and increase deaths, by dramatically changing the demographics of who is infected. Without lockdown, the youngest and most mobile people are likely to be infected - with minimal/zero deaths since COVID mortality is incredibly age dependent.

Under lockdown, those people are at home and intermingling with family. The only 'social' activity is shopping for food, leading to an unnatural mingling of old and young.

I live in Ukraine which has masks and little else against COVID. In shopping centers particularly in the evenings there are essentially zero old people - they fear for their lives, as they should.

The most effective policy we could have adopted was 6AM-10AM public transport and shopping for the aged only, and everyone else from then on. Segregate the elderly population into the mornings and let the masses in in the afternoon. This might have required shifting school and work to later hours in the day for three months, which seems a minor inconvenience.

Nobody credible believes 20-25% is a likely threshold for herd immunity. You cannot Realistically in America isolate the old from the young and if the young spread it like wildfire the old get sick.

Literally everything in your post is as poorly considered. It's important not to spread misinformation.

It's 20%-25% of currently detectable antibodies, coupled with another 20%-50% from prior coronaviruses or other cross-immunity. That's the important distinction. The sum approaches the 50%-70% needed for herd resistance based on 1-1/R0. That's the point of this article.

A couple people suppose is not the same as proof

See: https://www.news-medical.net/news/20200731/Research-suggests...

In addition to immunity based on T cells, the HIT depends on how individuals are networked. The original 60-70% estimates were based on 100% of people being vulnerable and also a random distribution of individuals interacting. In reality a small fraction of the population will have many interactions and once they become immune those transmission vectors away and the average R number drops. So based on the latest research plus observations of the worst hit places, 20-25% seems plausible.

Why are you assuming young people don't live with old people? It's extremely common.

It's rather uncommon in most European countries:

https://ec.europa.eu/eurostat/documents/3433488/5579620/KS-S...

Looking at this data for the US, it could be a factor for COVID mortality being higher in minorities:

https://www.pewsocialtrends.org/2010/03/18/the-return-of-the...

Your data actually says the opposite for Europe - it's highly dependent of the country of course, but if you look at page 6, in Southern countries - Spain, Italy, you have >30% of old people living with larger family (columns 'living with partners plus others' and 'no partner, not living alone'). That comes out at <10% for Nordic countries (Finland, Sweden etc)

Three-generation house-holds or households where adult children live with their older parents are very uncommon in most, but not all, EU countries.

The numbers you cite are explained by old people living in retirement facilities or coliving arrangements, but that doesn't imply cohabitation with young people. Under these circumstances, special precautions can and must be taken.

Please, please, stop reading and sharing hysterical news reports and go right to the data.

Here's daily deaths in Spain:

https://i.imgur.com/G84d20p.png

All numbers about total reported cases from the spring are going to be way, way off. There simply wasn't enough testing.

Deaths do not lie, which is why we should focus on those numbers. And by those numbers, this is in no way a repeat of Spring for Spain.

It's not a repeat of the spring...yet.

The daily number of cases in Spain appears to still be on the rise, and the death curve is usually 3-4 weeks lagging the cases. So deaths is likely still on the rise.

All that said, it may not reach the same proportions as the spring. But it is too early to wave it off either.

I'm afraid I don't follow.

Sweden didn't lock down because they wanted to achieve herd immunity quickly, while still taking measures to protect the most vulnerable. Spain locked down, actively attempting to minimize the spread of the virus.

How is the failure of Spain to achieve herd immunity (while actively attempting to achieve the opposite) a counterpoint to the Swedish example?

> Sweden didn't lock down because they wanted to achieve herd immunity quickly

This is a popular myth. There are no such statements (no not even from internal communication and similar). It was never a “strategy”

"In August, emails between the two men from as early as March show how they discussed herd immunity to limit the spread of the virus in Sweden." - Newsweek: Sweden's 'Herd Immunity' Mastermind Gets Promoted by WHO

https://www.newsweek.com/sweden-herd-immunity-mastermind-who...

One email thread out of thousands released where they brainstorm theories and predictions. Doesn't mean it's the official strategy and Giesecke is not even employed by FHM but retired.

These were exactly the emails I mean. Anyone who reads them can clearly see there is not even a slight suggestion that reaching herd immunity is somehow a possible “strategy”.

> Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and now is having a severe outbreak again[2]. What explanation is there other than herd immunity not having been reached?

The outbreak in Spain isn't as severe as you might think, there's a lot more positive tests, yet a lot less illness.

Herd immunity just means that R=1 without precautions. I would agree that Spain hasn't quite achieved herd immunity, but spread right now isn't anything like earlier this year.

One could speculate that because Spain went into such a strict lockdown, herd immunity could not be achieved, or that herd immunity was achieved, it just didn't last because COVID immunity doesn't last.

Antibody testing is getting tricky now, because antibodies are starting to fade, so unfortunately seroprevalence numbers will become underestimates with time.

That being said, in one hard-hit area of Stockholm, seroprevalence was 19% (https://www.folkhalsomyndigheten.se/publicerat-material/publ...). Stockholm as a whole has about 11% seroprevalence in their most recent numbers, but again, I believe antibodies are starting to fade now (https://www.folkhalsomyndigheten.se/publicerat-material/publ...).

more effective contact tracing.

There's no official national contact tracing in Sweden. Every region does it differently and some not at all.

That's not evidence of herd immunity thresholds being wrong though, that just opens up questions that need answers. Plus, the % positive rate doesn't seem to show a trend over the last 2 months, so I don't think your initial premise of "cases have been declining" is true.

https://ourworldindata.org/coronavirus/country/sweden?countr...

Because social distancing is only one part of equation.

Sweden has managed to address some of its other issues related to spread & fatalities. Notable among these are nursing homes, which had been a key source of spread. Once proper precautions were taken, they have stopped being as much of an issue.

That said, Sweden isn't out of the woods: The current trends are flat at best, and perhaps have a slight upward cast to them for new infections over the past few weeks.

> Notable among these are nursing homes, which had been a key source of spread.

Because so many different people visit those? Nursing homes have been key source of death, but not of spread.

Key source of spread are e.g. Prostitutes. Prostitution is (used to be) legal in e.g. Germany (afaik, in Sweden they intent to curb Prostitution by fining the client), but has been (temporarily) banned during the epidemic. That, of course, doesn't stop the custom, just moves it underground where the health of the providers cannot be monitored. Alleviating the financial problems of the providers might help curb the custom (as has been attempted in Germany afaik), as well as scaring the clients (as the state and media are doing their darnedest of).

Yes, nursing homes. Just look at the rates of health care workers in them getting sick. It spreads.

Besides, I gave that as one single example that helps explain Sweden's infection trends. I wasn't trying to comprehensively enumerate the many steps Sweden has taken to address COVID-19 without strict shutdown. I gave an existence proof of the possibility that your claim of herd immunity isn't the only possible explanation.

This is especially true given that other countries have not all had experiences in keeping with herd immunity.

The fact is that we still know too little about this puzzle. But every time a new piece comes out, everyone rushed to jam that piece into their own pre-conceived ideas.

> I gave an existence proof of the possibility that your claim of herd immunity isn't the only possible explanation.

My what? What else did you read into my text which I didn't write?

> Because so many different people visit those?

Yes, you can have temp workers that work in 5 facilities in a week, especially when staff starts falling ill and even more temp staff is nedded. The staff situation in Swedish elderly care was already a mess, and the pandemic just exposed some of the flaws.

> Lockdown didn't become stricter. People didn't become more compliant; rather the opposite.

> What explanation is there other than the herd immunity thresholds being wrong?

Let's start with sources on those first items before we get to an explanation.

My general understanding is that Sweden recommended certain things but never technically enforced anything, so I'm not sure what "compliance" means.

https://www.google.com/covid19/mobility/ says lockdown compliance has not changed much in my area and is trending slightly down if anything. I'm not aware of data on mask usage in my area, but a lack of confirmed scientific data shouldn't paralyze us; that results in problems like failing to recommend mask usage.

> but a lack of confirmed scientific data shouldn't paralyze us

Huh? That was not the point in contention. You said "the only conclusion is that the herd immunity numbers must be wrong" but have shown no evidence whatsoever to back that up.

You're putting words in my mouth; I did not say that at all. I asked "what explanation is there". I think a good discussion has resulted with some good points being made and some good data being shared.

One possibility is that better air circulation in closed rooms due to open windows, higher vitamin D levels, and people meeting others outdoors rather than indoors more often have been contributing factors. These ameliorating factors would play less of a role in Southern countries like Spain or Italy, since they were already present in spring in those regions and so all infections took place in spite of them.

Covid could be "lightly seasonal", so-to-say, though by far too infectious to be as seasonal as influenza. This is speculation, of course, unless it's backed up with studies.

By the way, maybe I'm mistaken about this, but it seems to me that any increase of the number of immunized people will statistically decrease the R-value even long before herd-immunity is reached. Together with the measures and heightened awareness this might also explain the data.

Even taking this seriously: Sweden has seen 570 deaths per million so far. If that toll represents the transition to effective herd immunity, then we'd expect another 3-4 million people to die worldwide before this burns itself out. And... you think that's a good thing? Sweden's response has been a disaster any way you cut it.

No.

The age-stratified IFR is magnitudes different between people under 40 and people above 70. You can still achieve herd immunity without infecting the vulnerable.

We have become better at treating patients with time as well, we now know that putting people on ventilators is a phenomenally bad idea, oxygen, steroids, and blood thinners is the way to go.

Also, the death rate in the US is higher than in Sweden, so how are those lockdowns working out for you?

The US population is unhealthy with bad health care on average. 42% are obese. It's not Lockdown leading to greater mortality.

The US? I'm not aware of any place here that's under lockdown.

Oahu in Hawaii is currently under lockdown until September 23rd.

Huh, you're right. Apparently there is limited hospital bed capacity on the Hawaiian islands.

As long as schools are closed you have at least a partial lockdown. Schools are still mostly closed in California, no?

yes, california is in arbitrary lockdown, closing many businesses and amenities that basically don't contribute to spread, rather than tackling the much harder but much more effective challenge of restricting (large) private social gatherings (where social norms actively discourage preventative measures like distancing) that are driving the spread (outside of hospitals and care facilities). our state "leaders" don't want to take the political hit of actually doing the effective rather than the performative.

If you count excess mortality then California has 60% more deaths than registered covid deaths, as can be seen here.

https://www.nytimes.com/interactive/2020/05/05/us/coronaviru...

If we take that into account then California actually has more deaths per capita than Sweden, and people are still dying in California so it will only get worse. So I agree their strategy was not all that good.

yes, as a resident, i can't tell you how frustrated i am with the inanity of it all. so much talk and bluster, so much performance, so much (lower- and middle-class) socioeconomic damage, yet so little effectiveness.

> Also, the death rate in the US is higher than in Sweden

Is Sweden comparable to the US? The population is more like a US state. Let's take Oregon as an example. About half the population of Sweden, and less than 10% of the covid deaths. We're not exactly locked down, either.

We're doing individual states? Cool, let's look at the northeast.

Massachusetts, Connecticut, and Rhode Island all have a total covid-19 death rate that's more than 2x that of Sweden.

Currently, the average daily cases is 5x higher in Rhode Island than in Sweden, 3x higher in Connecticut than in Sweden, and 2x higher in Massachusetts than in Sweden. The current daily covid-19 death rate in both Massachusetts and Rhode Island is higher than in Sweden.

> We're doing individual states? Cool, let's look at the northeast.

great, but what's the point? That Sweden is doing better than about a third of the United States?

The original point being made is that it's apples to oranges to compare the U.S. as a country to another country that it dwarfs in every population metric if you're looking at how to shape public policy.

In other words : There doesn't seem to be a one-size-fits-all solution for nation-wide policy making regarding a pandemic that fits every culture in the world.

I don't think that this surprises anyone.

Oregon does have a mask mandate. Wildfires are forcing most sane people indoors. Schools are digital at the moment. Lots of people working from home. There are definitely mitigation measures being taken in Oregon.

>What explanation is there other than the herd immunity thresholds being wrong?

Just to give two possible alternative reasons:

- outdoor life over the summer, leading to higher vitamin D levels;

- older people are more likely to still be living in their summer cottages.

Have you noticed that the death rate is possibly creeping upwards again? It’s simply too early to say.

When I arrived back in Stockholm (from the countryside) three weeks ago, the town was very empty: our family was alone eating lunch in a central Italian restaurant on a Sunday. Now the streets are full again, but covid takes 3-4 weeks to take hold again.

Not that I expect to see the levels of sickness from April again. But there’s a long winter still ahead of us.

I got another data point that (potentially) supports your claim. Peru here. Highest death per million habitants in the world (not the numbers reported by the Ministry of Health that is artificially reducing the numbers).

In Perú we are (sadly) keeping track of the pandemic by comparing the daily death count from previous years with the one for this years. You can safely assume: - there is no contact tracing - adherence to mask usage is good - social interactions are generally avoided with the usual folks that don't pay attention and an increase in those interactions every week.

These are the "death curves" of every region:

https://imgur.com/a/CWiUPiC

This is what happens when your government does not do anything and pretty much every one gets infected and your healthcare system collapses. You get a high spike in daily deaths and then a sharp drop (Lima is a special case for many reasons - size and geography).

Heard Immunity in every region (except Lima - yet). Seroprevalence studies are on their way...

Maybe people in Sweden have less physical contact (hugs, etc) than in other countries?

The joke says "Now that covid is less prevalent, scandinavians do not need to follow the 2m constraint .... and go back to their usual 5m"

MY assumption would be that it's a combination of nice summer weather which makes social distancing easier, and all the super spreading idiots that don't comply are getting sick, recovering, and no longer able to (for the time being) continue to infect others.

Without any details about "your area" it's impossible to say. We'd need the raw data, not your anecdotal "things are better".

He's talking about Sweden as a whole. There's nothing anecdotal about it and the raw data is one Google search away. Sweden currently has one of the lowest death rates in Europe.

In the Netherlands cases have been skyrocketing for weeks though.

The COVID "new cases" data for New York state seem to show something like herd immunity, despite numbers that should be well below herd immunity.

I suppose it could be something else, like New York residents being more diligent about masks, social distance, etc. Anecdotally, though, that doesn't seem to be the case.

NYC still seems like a ghost town to me.

Could be something like people with behaviors consistent with a higher risk of catching/spreading it being already immune by now.

That is a factor in herd immunity though.

Almost no one is wearing a mask in Sweden, and the current daily numbers look a lot like NY and NJ.

Partly NYC is relatively empty and relatively cautious since it was present and real, but partly it’s likely many times more folks have had it in NYC than has been widely reported, possibly one or two orders of magnitude more, leaving fewer candidates now.

If, back in the spring, you worked backwards from NYC deaths using mortality rates within the lowest ranges in US studies, then it seemed likely that before summer infections may have already approached most of the population.

Mortality rates of 0.5% would have a far higher number of infected, as noted in this April suggestion of much wider prevalence, which if the case ”the real number of infected people in LA County would be 28 to 55 times higher” — https://www.webmd.com/lung/news/20200424/more-data-bolsters-...

Aside from that math, a variety of sources suggest perhaps 25% of New Yorkers infected in April, such as:

A claim in June of ”roughly 25% by June” — https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-yor...

A July claim (opinion piece, not an epidemiologist) of an even earlier peak, Feb and March: ”With a city population estimated by the Census Bureau at 8,336,817, the 22.7% prevalence from the late-April state survey would mean that nearly 1.9 million New Yorkers had already contracted the disease as of early April.” — https://www.bloomberg.com/opinion/articles/2020-07-23/new-yo...

A July claim that ”over 60% of residents in some boroughs tested positive for the virus.”: https://abcnews.go.com/Health/nyc-neighborhoods-obtained-her...

Underappreciated, and insightful comment. I appreciate the insight and references, and did read all of them. Thank you.

There’s a naive equation for herd immunity which takes the unmitigated transmission rate or R0 of ~3 and calculates 1 - 1/R0 = .66.

This is the upper limit on the threshold (what I call the “naive herd immunity rate”) assuming there are no unaccounted for effects which would otherwise reduce R0.

Improved personal hygiene, social distancing, PPE, contact tracing, are all various behavioral ways that we have reduced the transmission rate below 2, which reduces the herd immunity needed to get transmission below 1 as long as those measures persist. Another way to say this is that if social measures get us to 1.3 then the infection still spreads until ~25% are infected.

The natural immunity discussed in the article is effectively a free boost to your current herd immunity rate. If serological studies show 20% had been infected, but then you can add another 30% on top of that, you are effectively already at 50% herd immunity.

I’m not sure what you mean by starting from a happy assumption. The real world data shows us that there is irrefutably something working to either reduce R0 or effectively boost the herd immunity level which isn’t showing up in the serological studies. TFA refers to several studies which show scientific evidence of a biological process that can explain what’s happening in the real world.

We can accurately estimate the Rt by just looking at positivity rates, test count, and positive case count. Either R0 is much lower than initially calculated, or effective immunity level is higher than serology tests have shown. I suppose you can pick one, but Sweden at least is a strong datapoint that it’s a function of immunity not social suppression measures.

And then factor in that about 1/2 of all Covid deaths (in the US) are in people over the age of 75 (a population of just 22m).

A focus on vaccinating that demographic will quickly, dramatically reduce the mortality rate of Covid.

Out of the 104 million people under the age of 25 in the US, only ~400 people have died from Covid.

Out of 220 million people under the age of 55, there have only been ~15,000 deaths.

We have a very blatant demographic target that we can focus on to rapidly knock down the mortality rate.

The main challenge for vaccines is currently the R+D, not manufacturing enough doses.

The mRNA vaccines being tested may need down to -70°C cold storage during transport and immediately before use, so quite a logistical challenge. Prioritizing those most at risk will be critical to knocking down the CFR dramatically.

> to -70°C cold storage during transport and immediately before use, so quite a logistical challenge.

Liquid N2. The same is done, e.g. for bull sperma. This isn't an insurmountable challenge.

Liquid N2 is common in industry. There are national and local companies with branches scattered all over the US that can supply liquid N2 to anyone equipped to handle it. Since doctors use N2 (to freeze warts) they know how to deliver medial grade N2 (if there is such a thing). Those suppliers will work with their normal customers to ensure medical use gets what they need (if arranged in advance they can produce less in exchange for a vaccine for their employees which ultimately means better profits)

That is N2 isn't a supply problem. However there are other logistical problems. Most industry uses of N2 are in very large quantities and so the ability to fill a millions of vial sized containers of N2 might not exist even though more than enough N2 exists.

Dry ice is -78°C so perhaps that could work?

We do not know that. The are several promising vaccines in stage 3 - that means R&D is over for them and has been for a while. If in the future we learn they work then the problem today is scaling manufacturing/delivery not R&D. Of course if it turns out they don't work then R&D remains the problem. We don't know which future we are in today.

The Oxford vaccine is being manufactured now, they aren't waiting for R&D to finish before they start.

Not in enough quantities to vaccinate the world. This quantity is a hard problem.

I think they are planning 2 billion doses, I’m not sure how long that will take though.

How does one focus on vaccinating the elderly without a vaccine? I mean, you're not wrong in principle, you just skipped an important step.

If you look at Atlanta cases are way down and everything is open. People go out to bars, nightclubs, strip clubs, etc. There is not much social distancing and only place I see people wear masks at is the grocery store. I feel like a lot of people that get it and are younger don't get tested and just stay home and ride it out. So the actual cases vs reported cases are a lot higher.

> the estimate death toll is reduced to 1/15th (6.6%) of the original estimates

A million people are dead of this virus already. Which "original estimates" are you citing that predicted 15M people dead? Those line up with the absolute worst case scenarios, not actual predictions.

Well,... for example, the National Institute for Health Research University College London predicted ~580k excess 1-year mortality in a "do nothing" scenario in their "high" relative-risk (RR) assessment. That's ~0.9% of the population in 1 year, or 70 million people if extrapolated worldwide.

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

Oh, and just for fun, this is MSNBC yesterday;

“ Math on Trump Covid strategy has millions dying before it works”

“2.97% fatality rate * 215,000,000 = 6,385,500 dead”

https://www.msnbc.com/rachel-maddow/watch/math-on-trump-covi...

"The original estimates"

Look at this range of epidemiologists' 2020 death toll estimates (second chart below), gathered by 538 on April 2nd. Comparing to the current death total of 200k in the US, It's actually pretty decent, the majority of experts' ranges include 250k, which may be around where we end up in 2.5 months' time.

https://fivethirtyeight.com/features/best-case-and-worst-cas...

I would take any cruise-ship analysis from early on with a grain of salt. It's very hard to test a pandemic extremely early on, there are less valid and reliable testing instruments.

Michael Levitt has been saying this since the Diamond Princess event.

Scratch that - he hasn't been maintaining there's pre-existing immunity, rather asking the question to anyone who'd listen...he doesn't have a background in biology, but that's one of the few conclusions he could surmise from studying the data.

It is encouraging that real scientists (not just "pro-science" laymen) seem to be listening to these ideas and producing studies on them while the media ignores and ridicules them.

https://www.latimes.com/science/story/2020-03-22/coronavirus... He seems to be a perfect example of the axiom that deep knowledge in one field doesn't necessarily give you expertise in others. Seems like he should leave Epidemiology to the epidemiologists.

bingo. Maybe why actors should stick to acting ?

Since when is that an axiom? He carefully analyzed the data and presented a falsifiable prediction along with his methodology. If he was wrong we should look at why and learn from it. (Did he fail to account for the virus mutating, could different regions have different co-morbidities or immunities?)

We should not rely on appeals to authority, those expert epidemiologists didn't do much better.

He's been talking about this a lot - the (lack of) communication and debate in the science community.

People interested in truth invite criticism: "Please give me contrary evidence! Show me I'm wrong!"

"Show me I'm wrong" is not the starting point in the scientific method.

It's something that's felt by scientists who've developed a hypothesis they want verified. Keen interest in explanations of data, etc.

It kind of is. Hypothesis rejection is the primary means of advancing knowledge.

"We tried to prove this hypothesis wrong and could not" is the main thing you want a study to do. Having everyone try to prove your hypothesis wrong, and failing, is the main way that science advances.

No, science proceeds on the basis of trying to prove a hypothesis is correct. As in, I hypothesize A should B, evidence XYZ supports this.

You accomplish very little trying to prove a hypothesis wrong, because most are.

While you are correct conceptually, most scientific research using statistics does in fact attempt to provide evidence against no-effect (the null hypothesis).

The p-value of a scientific study is the probability that the given data would have been observed, given that there is no effect. Hence why small p-values can be associated with the success of the alternative hypothesis (i.e. what a scientist actually thinks will happen).

We should remember Popper (1).

You can't prove an hypothesis is correct. All models are temporal until they are disprove.

(1) - https://en.wikipedia.org/wiki/Falsifiability

I know some people who tap a can of Coke before they open it, because "that prevents it from spilling". Each time they do that, they are more convinced that their hypothesis is correct.

But is it correct? To find out, we need to try to invalidate it. Try opening the can without tapping it first. If the Coke doesn't spill, the hypothesis is clearly wrong. It the Coke does spill now, it's quite strong evidence in favor of the hypothesis.

Lol no ! You prove a hypothesis to be correct.

No, really, it is not. In your own example you're already jumping to testing a hypothesis. "Scientific method" isn't just a vague phrase, there literally is a specific method of steps to go through.

The first step is Observation. Sometimes split out into Observation, then Research.

Then comes the formulation of a hypothesis.

After that is constructing a way to test the hypothesis. Not to prove it wrong, not to prove it right, but to test it.

There's more after that, it's an iterative process and a single test of a hypothesis isn't always definitive, often it is not. But "Prove me wrong" is not the starting point.

> those expert epidemiologists didn't do much better.

How did you arrive at this assessment? I've been following this since the end of January, and every expert I've heard gave sound and very good advise based on the available evidence at that time. Some of them might have made some disputable trade-offs, for example the Swedish lead epidemiologist, but overall there was a lot of agreement and the recommendations were excellent.

Okay, maybe there are a few outlier countries like the US and Brazil where there might have been political muddling of the expert messages. Be that as it may, in general the advice from experts was not only good, most countries also succeeded in controlling the spread of the virus based on it. (And not every country needs to implement the same measures to be successful in that, it's more about a mix that works in that country.)

Those experts at the WHO predicted, in March, that if Sweden does not enforce a lockdown as recommended by the WHO, it will have 96,000 deaths on 1-July.

The non-expert Michael Levitt, predicted at the same time, by fitting 3 parameters of a Gompertz distribution (And no other knowledge), that Sweden will have 5000 deaths on 1-July if things continue as they were when he made the prediction (that is, no WHO recommended lockdown).

I'll leave it to you to lookup the Swedish death count on 1-July to see if the expert epidemiologists from the WHO had a better idea than non-expert Levitt. (But I'll give you a hint: It is mid september, and Sweden has ~6000 deaths).

Nonsense, and also irrelevant. You're picking out one predictive model that got it wrong. I'd like to see this model, by the way. I've seen numerous models that got it right, and in any case I was talking about the advice experts gave. Nobody doubts that Sweden's death toll would be much lower if they had done a lockdown like almost every other country. In fact, the Swedish lead epidemiologist admitted that mistakes were made and that they failed to protect the elderly.

The WHO advice was much better than what Swedish advisors came up with.

Besides that, I was not talking about WHO experts but about experts in general. Every country has them, and they supply the data to WHO.

Last but not least, you cannot evaluate a model on the basis of a singular prediction.

From a medical perspective, 'immunity' means triggering any immune system response, not that someone will not get or have symptoms of a disease.

This is an important nuance that has muddled research for lay people during the pandemic.

Edit: Definition of Immunity - https://medical-dictionary.thefreedictionary.com/immunity

No it doesn't. It means to resist harmful infection.

If you catch a serious disease, like HIV, malaria, etc, and you die, you have an immune system response - it just failed.

Even people that die of COVID had an immune system response. It just couldn't cope with it.

The somewhat frightening thing is that our immune system, literally right now, is fighting the good fight and saving your life.

One of the confusing aspects of AIDS is that you don't die from AIDS - you die from the opportunistic infections that happen from not having an immune system.

My understanding was that the immune response was responsible for a lot of the harmful effects of covid in the first place. I thought the virus itself wasn't actually causing mass cell death?

I'm not a doctor or anything, but there's also reports that a "vitamin D hammer" has dropped death rate from 86% intubated patients to 36%, and vitamin D triggers a huge immune response. So my guess is that it's either NOT an immune response, or a bad one, until you add the Vit. D.

It looks that way. It has drifted from cytokine storm to bradykinin storm (discussed not long ago here on HN).

https://www.medpagetoday.com/infectiousdisease/covid19/88560

https://elemental.medium.com/a-supercomputer-analyzed-covid-...

Triggering a response means your body has recognized something that isn't itself. In doing so it defends itself.

This is immunity, even if it fails or causes more damage than good. It is fighting the foreign agent.

A response is not immunity. Immunity is more than just a response to something. That difference is actually encoded in things like vaccine testing process: earlier tests ascertain whether or not the immune system responded in any way. Later tests focus on whether or not that response produced some level of immunity.

But it also should mean that the "immune" will not spread the disease much at all -- certainly not as much as the not-immune who get sick. This is the key thing about immunity.

Also, though (re)exposure of the immune may trigger an immune system response, the individual might not notice the exposure or the immune system response.

Immunity has nothing to do with ability to spread. It only relates to self.

'immunity' means triggering any immune system response

The exact definition you cite does not support this. It begins by very clearly saying it is a state of being protected:

Immunity: the condition of being immune; the protection against infectious disease

Right now, this seems to be the best explanation for a lot of the unexpected observations we made so far:

* few children seem to be sick from that virus * geographical disparity in Europe (compare northern Germany vs. northern Italy), even considering population density * the high number of reportedly asymptomatic cases * uneven distribution of infectiousness ("superspreaders")

My pet theory so far is that one or more very similar viruses have been in circulation for a while and that "asymptomatic" carriers of COVID-19 are in fact at least partially immune due to exposure to these similar viruses.

Note that this also means that COVID-19 is much scarier than it looks. Because if you are not among those with prior immunity, you are much more likely to suffer from the bad effects of that virus.

I keep wondering if the immunity to these viruses disappears while in lockdown causing a much more severe second wave than expected...

Don't know why you were down voted - I take your position to mean "has lockdown led to a loss of general immunity due to lack of exposure to general pathogens" which I think is a valid question to ask.

Seems some people are too trigger happy and unwilling to explore charitable interpretation of posts.

Precisely, it’s not as if we don’t know from other pandemics that the second wave is almost always more severe... I’m not suggesting we go full Sweden and start coughing on each other in the sauna, but there are lots of factors we are struggling to account for in all this.

The article and your wondering doesn't provide enough evidence that we should go counter to not trying to spread the virus in the first place. Social distancing, hygiene and a vaccine are much more definitive ways to combat a severe second wave than hoping magically some people have built-in immunity or some unknown environmental trigger results in a similar immune response.

The parent never suggested anything anti-lockdown. At face value it is merely questioning the existence of a possible trade off of lockdown. As you've not provided evidence or anecdotal stories to refute the question I'm still in no better position to consider the parent's question with more information.

I mean if we really want to start projecting our own agendas or anti agendas, the whole notion of "evidence" leaves a bad taste in my mouth given the WHO went on record saying "there is no evidence of human transmission". And I am saying this as a scientist!

Our obsession with evidence and data is important (as what are we without empiricism) but boy has it seemed more like a curse rather than a blessing at various stages throughout this pandemic. I am definitely team Bayes on these matters, common sense and experience do hold some value sometimes.

Germ theory and the science around vaccines is well established. Winging it because maybe some unknown might protect us sounds absurd. To get to the point where the existence of this unknown can be proven yes/no will take longer than it will to develop a vaccine.

I never questioned germ theory nor the science of vaccines.

I do raise an eyebrow however when there's so much rigmarole around "evidence" and mask wearing. Just like there was rigmarole around hand washing when Semmelweis promoted it. What a bizarre hill people have made to die on.

And how slow the WHO were to declare the dangers of covid in its early stages.

It's a bad theory with no medical evidence.

The answer is probably "we don't know." The closest example I can think of for this is what the immune systems of ISS astronauts look like after 6 months in orbit.

Listening to epidemiologists alone was/is a bad choice because they study the spread of disease. You also to consider long-term effects on the immune system, the economy, education, social structure, politics.

The second-order effects have already been surprising:

- Social unrest in the US - China restricting freedoms in Hong Kong - Bifurcated "K" economy - Covid case surges in countries that "did it right" with hard lockdowns

My pet theory is that chronic disease like obesity, combined with pre-existing immunity, and possibly some correlation to vitamin-d deficiency explains most of how this has played out.

Factor in a glut of people who're living into advanced age, due to the progress of medical technology, so naturally in a precarious place against any infection. And of course, mismanagement of those people in nursing homes means guaranteed disaster.

So really, I think it's much less dangerous than we've let on, but deadly to certain demographics, that happen to be larger in the West (obese, diabetic, etc.).

This doesn't pan out when children have developed severe inflammatory responses, young adults have died, and not all people with comorbidities have had severe reactions. You can't just say it's fat and/or old people who are having severe symptoms or dying.

It mostly does. Those cases you mention are quite rare.

>This doesn't pan out when children have developed severe inflammatory responses, young adults have died, and not all people with comorbidities have had severe reactions

How many millions has covid infected thus far? It would be concerning if it hadn't killed a couple healthy kids and not killed a couple obese old people.

It's not "a couple", there's been about 105 child deaths, and 4600 child hospitalizations. It's not as bad as adults, but you can't say little Johnny is magically immune, nor can you say that Brad the football star at the local college is either. I don't think it's currently clear why some apparently healthy people develop severe reactions.

Do you feel we should restrict billions from gathering with and hugging their family so that we can save 105 children?

Can you help us understand the thinking you use to make that tradeoff?

The point of the 105 dead children was to show children can be severely affected and don't have magic immunity. 500K children have been diagnosed with COVID, with varying symptom levels. We have 200,000 dead overall in the USA, so it's not just a matter of 105 dead children justifying lockdown, it's all those other dead people you seem to have forgotten about.

Also FYI, you can't hug your family member anymore once they're dead.

What’s the median age of those that have sadly passed and the percentage with comorbidities?

Do you really mean "sadly" when trying to make the point that old people or people with pre-existing conditions are acceptable deaths?

He is Just Asking Questions

https://rationalwiki.org/wiki/Just_asking_questions

Am I. Which part of the question is leading? Which part is not Socratic?

Well that would be an extremely unpleasant attempt at putting words in somebody's mouth that makes me wonder whether you are actually engaging honestly here.

Did you honestly not know the answer? What was your point?

They don't, but they are far more susceptible to Measles. In 2018 140,000 children died from measles -- a disease we actually have a well known vaccine that's been proven safe!

Well we've yet to develop a COVID-19 vaccine that ditzy parents can ignore/avoid. Stupidity isn't an excuse for more stupidity.

This is emotional manipulation that we can all engage in. The 105 children are not the only victims.

I have bad asthma and my wife is ill I don't appreciate you gathering and hugging your family and killing mine.

Did that advance the discussion? Was it manipulation? No and you bet!

It's small enough that it's not a concern and not something we should spend much effort worrying about. 105 is absolutely nothing compared to nearly 200k deaths in the US.

It's also a HUGE distraction to the real concern: We don't fully understand how contagious children are.

We have to look at the bigger statistics. Some young children die of many things that the vast majority of them easily survive, but that doesn't mean we need to lock down every flu season.

Flu is harder to transmit and there is vaccine infrastructure available every year, despite that, it can still be very severe. Let's add a coronavirus with potentially greater severity than a flu, which has no vaccine, and has easier transmission, with a severe flu season this year and just watch the bodies pile up.

> with a severe flu season this year and just watch the bodies pile up.

There is no evidence of this and you are continually creating worst-case scenarios.

Please stop.

Do you know that this year will not be a difficult flu season? Do you know the ramifications of combined flu and COVID-19 infection?

If the flu season is severe, then it could be quite catastrophic when combined with COVID-19. We should definitely be preparing for worst-case scenarios, and not downplaying potential severity because it's inconvenient.

Influenza and Noro/Calicivirus (Winter vomiting disease) stats for Sweden this year. Social distancing and increased hygiene measures implemented mid March, about week 11, killed them off much earlier than usual.

Influenza: https://www.folkhalsomyndigheten.se/globalassets/statistik-u...

Calicivirus (Vinter vomiting disease): https://www.folkhalsomyndigheten.se/contentassets/0ad710ef37...

Technically that was "last flu season", not the upcoming flu season, and it was relatively mild. It is hard to predict if 2020-2021 will be similar, or 2017 levels, or 2009 levels. At minimum it will add more strain to medical services.

It shows that "okay" measures against COVID are strong enough to push the R_eff value for those viruses well below 1, unless something extraordinary happens. I.e. no extra strain for medical services.

As said, this hinges on social distancing and hygiene measures being kept enforced. If you open a country fully again and get two simultaneous peaks then you are in for a bad time.

I think we're on the same page here. My catastrophic scenario involved no mitigation steps and removal of lockdown. The goal was to dissuade people from thinking since things are "fine/better" right now, lockdown/mitigation is not needed anymore. We still need to get through this winter, and on to a vaccine.

"The southern hemisphere skipped flu season in 2020, Efforts to stop covid-19 have had at least one welcome side-effect"

https://www.economist.com/graphic-detail/2020/09/12/the-sout...

My point to jaywalk was that combined COVID-19 + severe flu w/o mitigations like a lockdown, could be catastrophic. Their post was anti-lockdown comparing COVID-19 to flu.

I am not surprised that measures to avoid COVID-19 also reduces the spread of flu.

I wonder whether skipping flu season is alike fire suppression in forests. When, not if, it eventually burns, it'll be that much more devastating.

Go here: https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm

Filter by 'Weekly Number of Deaths by Age' and you will see that it is literally the safest time ever for children and young adults because they are not allowed to go outside and do dumb stuff. Yes, some of them have died because of COVID, but the number is staggeringly small.

Maybe fewer have died of covid because of lockdown?

Sweden didn't close schools, 1 person under 20 has died out of about 2 million.

How many people do people under 20 infect?

How many of those secondary infections die? How many of them stay sick for months?

There was a case right before schools opened in Georgia, I believe, of a kid who caught COVID at football practice. He's fine, but both of his parents died in a week.

Fortunately, he now no longer needs to worry about COVID. Unfortunately, he's now an orphan.

And he's still proof that "few children get sick" from this.

Children get sick, few have got sick enough to have died from it.

I did not realize that the sole metric that our society should optimize for, to the exclusion of all else is 'how many children get sick and die from COVID'.

(It's a very convenient optimization metric, though, because it requires us to do quite literally nothing.)

Lots of people argue that children aren't dying because they were more locked down. For example the person I responded to. That is wrong, children aren't dying since covid doesn't hit them very hard. Children being vectors infecting others wasn't a part of this discussion.

No. "Obesity" and "vitamin-d deficiency" can't explain what happened in Italy (a lot of sun), and also can't explain what happened in the Nordic countries (much less sun), including Germany and Sweden (the later having order of magnitude more deaths than the former, measured as the percentage of the population). Sweden is particularly bad, having the deaths per capita even worse than the U.S. the last time I've checked.

What we see is that countries that were lucky enough to do strong enough prevention actions early enough had order of magnitude less deaths than those who didn't do them (and Sweden is in the latter camp, even if they did have more response than most admit -- they did close all universities, for example). The scale of deaths seen in New York would have never happened, had the use of masks been common early enough.

Eidt: Regarding "vulnerable populations" Italy and Germany have similar number of "vulnerable" and it seems Sweden would be better than Germany then:

https://commons.wikimedia.org/wiki/File:Population_pyramid_o...

https://commons.wikimedia.org/wiki/File:Sweden_population_py...

It is worth noting that living in a sunny country does not guarantee the larger population receiving adequate Vitamin D through sun exposure, as many such populations somewhat paradoxically avoid sun exposure, as there are legitimate health reasons for doing so (extreme heat, concerns about skin cancer, etc.).

To support that you'd have to show that Italians have order of magnitudes higher deficiency than most of Nordic countries, and I don't think it is possible.

Another country with equivalent sun exposure to Italy is Greece, again orders of magnitude less deaths (like Germany). They also had strong lockdowns and early enough.

It's the measures. Analyzing what happened in Europe (and still happens) can't be explained with anything else.

Compare it with fires. Small fires are easy to extinguish. Pretending "it will go away" will simply result in a big fires. Eventually there won't be anything to burn. With people, eventually everybody who can and "feels the heat" will try to protect themselves.

A lot of older people in Sweden stay in their homes and take care not to be infected. Masks are common in the supermarkets, etc.

> Masks are common in the supermarkets, etc.

Not sure where you got this information - masks are not commonly worn at all in Sweden. I see perhaps 1 mask per week, unless I go into the city center, then I might see 10 in a day.

The Swedish public health authorities are not currently recommending general usage of face masks, citing mainly the lack of evidence of the effectiveness of general mask usage (wearing a mask can cause you to get lulled into a false sense of security, for example).

See https://www.folkhalsomyndigheten.se/smittskydd-beredskap/utb...

(in Swedish, unfortunately)

> To support that you'd have to show that Italians have order of magnitudes higher deficiency than most of Nordic countries, and I don't think it is possible.

Sweden adds vitamin D to food items so I wouldn't be surprised if Sweden has less vitamin D deficiency than many southern countries.

https://www.nutraingredients.com/Article/2015/05/28/Sweden-t...

Can we find order of magnitude difference among darker skinned people? We've all heard about the disparity there.

> Masks are common in the supermarkets, etc.

This is outright false. I've been to a big supermarket twice this week and didn't see a single mask as far as I can recall.

yes, masks are marginal at best, and as long as you're not spending a lot of time breathing another's direct exhaust, even indoors, you're at negligibly low risk of transmission.

i get super frustrated with the random corona rules at supermarkets in the US (like one-way only aisles, exit only doors), especially trader joe's, which is as draconian as it is arbitrary. for a while they weren't allowing you to take in your reusable grocery bags. later they relented and switched to just bagging your own groceries outdoors, leading to an awkward triple handling of your purchased items for what amounts to nothing other than safety theater.

for 6 months i've worn the same useless surgical mask to play my part in that misguided spectacle, when required. folks are slowly starting to realize their lack of utility, but have nothing else to latch onto because the obvious solution of modest distancing seems so mundanely unbelievable (and lacking obvious and spectacular conformance).

For reference, see this article in the Lancet:

https://www.thelancet.com/journals/landia/article/PIIS2213-8...

It's just an argument that the actual deficiency could cause worse outcome. But that article in Lancet doesn't claim that Italy had Vitamin D deficient population. The number of deaths per capita due to Covid-19 was however orders of magnitude higher in Italy and Sweden than in Germany. I don't think that there's anywhere any evidence that Germans are less Vitamin D deficient than Italians and Germans.

Vitamin D doesn't explain anything related to Covid-19 deaths in Europe, whereas the existence or lack of measures do, almost perfectly. Whoever can look at the curves of number of deaths since the begin of the epidemics, check the times of partial lockdowns or the introduction of some measures, can see that exactly around three weeks after these the curves stop going up and begin going down.

Italy as the first country seriously hit in Europe had the curve raising exponentially up until the measures started to work (there's a delay -- for people to stop dying the spread of infection has to turn first etc). Sweden also had the curve raising comparably to Italy, even if they had a negative example from Italy -- because there was a decision of targeting the "herd immunity". Germany's curve remained very low, as they had low prevalence at the time their measures started to be applied.

It's all about the measures and the adherence of the people to them.

Many countries have Vitamin D deficient populations, including Italy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986426/

In Italy, it gets worse the older the population gets.

It is also an issue in Germany: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499202/

I make no claims other than: 1) there is a very strong correlation between vitamin D insufficiency/deficiency and poor outcomes for COVID-19, and 2) many populations, including those in sunny countries, suffer from widespread vitamin D insufficiency.

I for one have been taking 1,000 IUs of vitamin D every day since March, and trying to get sun exposure mid-day whenever I can.

Look at the graph, it has obviously nothing to do with any deficiencies, and everything to do with the measures:

https://ourworldindata.org/coronavirus-data-explorer?zoomToS...

The comparison is possible because it’s per million. See Italy and Spain hit before they were aware what is going on., then introducing lockdowns.

See Sweden’s and the US denial, then limiting the initial outbreaks but continuing just not doing enough.

See Greece and Germany doing early enough good enough measures, and still doing it.

It’s that simple. The US not being aware how wrong they are doing is a crime to their own people. It’s historical failure.

You claim: “there is a very strong correlation between vitamin D insufficiency/deficiency and poor outcomes for COVID-19“ — show me that on the graph above. It’s obviously a red herring talking about Vitamin D once one sees it.

India being the case in point where exposed skin is culturally unacceptable

I said the interplay of chronic disease, vitamin-d and vulnerable populations.

> Sweden is particularly bad, having the deaths per capita even worse than the U.S. the last time I've checked.

No. USA: 608 per million. Sweden: 580. [1]

But the current trajectory is also important. In Sweden, the last day with more than 0.6 deaths/million was July 21 (according to actual date of death, not the date when death was reported), while the US currently is about 2-3 deaths/million/day.

[1] https://www.worldometers.info/coronavirus/

People really see what they want to see. As a Swede this whole pandemic has been truly enlightening regarding peoples propensity for confirmation bias. It has been truly shocking how prevalent it is throughout entire societies and ideologies.

Here in Sweden the right-wing folks want to lock everything down and the left-wing want to keep deferring it to the experts. In the rest of the world it seems to be the other way around.

Another way of looking at it: the left-wing people everywhere want to defer to the experts. It's just that the experts in different places are saying different things.

Can you provide some articles/material regarding right wingers wanting to lock things down in Sweden? I'm not familiar with Swedish politics and would be interested in reading more.

Throughout the pandemic the (neo-)Liberal (right-wing by Swedish standards) newspaper Dagens Nyheter (Today's News, dn.se) have led a campaign criticising the Swedish lax approach. The news site is paywalled however.

The leader of the Swedish Democrats, the most right-wing in the Swedish parliament, called for the state epidemiologist, Anders Tegnells, to take responsibility and resign immediately: https://www.expressen.se/nyheter/jimmie-akesson-tegnell-mast...

Interesting enough it's also the same kind of fringe-right that are protesting in against restrictions in Germany that is calling our approach genocidal here:

"Tegnell is a danger to society" https://projektsanning.com/2020/03/12/coronaviruset-statsepi...

"Tegnell reported to the Police due to the mass death among elderly" https://www.friatider.se/tegnell-polisanmald-massdoden-bland...

The debate is pretty calm compared to USA, most politicians agree with the general strategy so the opposition mostly criticize the execution.

https://www.thelocal.se/20200530/swedish-opposition-demands-...

I wish this complete upside-down debate would get more attention in international media but it's truly the reverse of what's happening in the US.

While the official stance for all parties is that they support the strategy (the most right-wing party being the exception who is heavily criticizing it), it's more telling in social media.

Hanif Bali, one of the most prominent right-wing figures in social media, has really been pushing for lockdowns/masks and is cheered on by his tail of alt-right followers. Meanwhile the left is mocking him, lockdowns and masks in general.

Sweden has 5x deaths of Germany. Not quite an order of magnitude. And as someone else pointed out, the US has more deaths per capita than Sweden.

> the US has more deaths per capita than Sweden

Nothing to be proud about for either of them. Anyway, until e.g. month ago Sweden had the lead.

Just checked: it seems the last day the U.S. was better than Sweden in deaths per capita was 11. September, so just 8 days ago. And, when the trends continue, in a week the U.S. will be worse than the U.K. too. The only countries in Europe with more Covid-19 deaths per million then will be Belgium and Spain.

If I recall correctly the US passed Sweden in excess mortality sometime in June/July. So they have probably passed some of the other European countries already. I couldn't find a good up to date source, but Belgium seems to have lower excess than US. Comparing death statistics is not trivial.

Anyways, I don't think comparing the US to most countries in Europe really makes sense, considering the size and population differences.

> If I recall correctly the US passed Sweden in excess mortality sometime in June/July.

According to ourworldindata, in reported Covid-19 deaths per million, on Sept 12:

https://ourworldindata.org/coronavirus-data-explorer?zoomToS...

> I don't think comparing the US to most countries in Europe really makes sense

You are missing "per million" which is what I used. Comparing absolute numbers has of course no sense. When comparing relative numbers ("per million"), the big country spread across big area, like U.S. is, would be expected have huge advantages compared to any country in Europe (due to slower spread over the distances, much less dependency on public transportation). Moreover, the countries worst hit in Europe were only those where the spread happened first -- others took note and introduced measures early enough. Not the U.S. which totally botched its response even ignoring the initial hit in NY. Compare the slopes of all other European countries for months, v.s. what's going on in the U.S. The response in the U.S. is criminally bad, and continues to be so -- and not looking at the "cases" but simply and tragically, deaths. Those that are reported.

I admit that comparing some other estimates of "excess deaths" could give some other numbers, but I don't see any way in which U.S. can look good, especially as it was Italy being hit the first and everybody else having the time to react somehow.

Also see daily average of deaths per million, to get the idea how bad it is still:

https://ourworldindata.org/grapher/daily-covid-deaths-per-mi...

5x is order of magnitude larger. Quote:

Generally, the order of magnitude of a number is the smallest power of 10 used to represent that number.[2] To work out the order of magnitude of a number N, the number is first expressed in the following form:

    N = a × 10^b

where 1/sqrt(10) ≤ a < sqrt(10) . Then, b represents the order of magnitude of the number.

https://en.wikipedia.org/wiki/Order_of_magnitude

There is now strong evidence that obesity and vitamin D deficiency are serious risk factors for COVID-19.

https://onlinelibrary.wiley.com/doi/full/10.1111/obr.13128

https://cardiologyres.org/index.php/Cardiologyres/article/vi...

https://www.mdpi.com/2072-6643/12/9/2757

>Factor in a glut of people who're living into advanced age, due to the progress of medical technology, so naturally in a precarious place against any infection

Then why does the annual flu not wipe out this population? Immunity lasts about 3 years so every such person who is exposed to the flu should be dying in one 3 year cycle.

Wouldn't annual re-exposure to a similar virus "renew" the immunity?

Flu vaccination is pretty prevalent among seniors.

Which reinforces the need to have vaccines to get to herd immunity, not just herd immunity except for seniors who will die a lot.

Immunity lasts longer than 3 years:

>According to our study, it appears they can last the entire lifespan of the human organism — 90 years plus.

>n our study we were looking for antibodies to the 1918 flu. This flu virus was reconstructed a number of years ago in the lab, so we were able to test to see if 90 years later we could still find antibodies. I recruited survivors, people who were born in 1915 or earlier and thus presumably survived the 1918 flu. We found that virtually all the people born in 1915 or earlier — about 90% of them — had good "titers" to the 1918 flu, which means they still had reasonably high concentrations of the antibodies in their blood, whereas among controls, people who were born in 1926 or later, it was only about 10%. That was really quite a remarkable finding.

http://content.time.com/time/health/article/0,8599,1835907,0...

It does, in recent years, the flu death tolls have been below average mortality - Levitt's been looking at EuroMOMO for this.

>one or more very similar viruses have been in circulation for a while

the genetic makeup of covid-19 has been well studied and this is not the case. If it were multiple different diseases, it would be very obvious.

I completely agree with this hypothesis, it explains why groups so disparate have all seen similar outcomes(low instances of severe covid:

-homeless

-celebrities

-children

What do all these groups have in common?

Age? well count out celebrities, ie. Tom Hanks, Prince Philip(both are in advanced age).

Good health? I'd count out homeless as a lot suffer from chronic ill-health.

Weight? Some heavier celebrities have had covid and been fine, its an important metric though.

Exposure to a lot of viruses? Yes, all three groups are in constant exposure to a multitude of viruses, from children in daycare, to celebrities interacting with tons of people to always traveling, to homeless getting exposed to viruses in trash and living in unsanitary conditions.

I've been wondering this since the beginning, as a parent of a relatively small child in preschool.

I've had one prediction all along, which is that parents of small children would probably also have lower rates of symptomatic disease, lower severity, etc. than matched controls, because they'd also be exposed to prexisting coronaviruses and therefore have some cross-immunity.

You could probably extend this to other groups too.

I admit it might be totally wrong but it seems straightforward to test with the right data, and if it were wrong that would also be interesting.

Let me post an informational link, with some explanation of potential increased resistance:

"[HCoV-NL63] is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to ACE2... Further analysis of HCoV-NL63 pathogenicity seems warranted, in particular because of recent evidence that this virus uses the same cellular receptor as SARS-CoV (ACE2)."

https://en.wikipedia.org/wiki/Human_coronavirus_NL63

Looking at situation in India which is extremely crowded in many cities, the number of cases and deaths is relatively is very low.

Many share the opinion that there is some sort of immunity among the population here.

Not sure about the scientific validity, but I'm inclined to believe that the lack of such immunity would have made the situation extremely dire by now.

A recent study in Mumbai found that 57% of slums residents were seropositive for SARS-CoV-2 antibodies, which indicated an infection fatality rate (IFR) of 0.05 - 0.10%. That's much lower than most other places and it's not clear what accounts for the discrepancy.

https://www.cnbctv18.com/healthcare/57-sero-prevalence-in-sl...

Any antibody testing done this year is pretty suspect. We simply don't know which tests have a high false-positive rate. Studies like that one should be testing the test but instead are trying to draw conclusions about the virus spread based on a test with unknown efficacy.

How do you know, that the test wasn't tested?

Most good seroprevalence studies combine the two.

Nope. They used the Abbott IgG antibody test which was validated to have 99.63% specificity and 100% sensitivity. There is no need for field researchers to test the test. Unless there was widespread contamination of specimens or something the study results are solid.

https://www.medrxiv.org/content/10.1101/2020.08.27.20182741v...

https://www.abbott.com/antibody-testing/top-COVID-19-antibod...

Young and thin people in the slums.

Another guess: Even the indoor areas likely have no windows/doors and have tons of fresh air. So even if you get the virus, it's likely a lower initial viral load which seems to be correlated with less severe outcomes?

Maybe, but it is VERY densely populated, so it may negate that effect.

i would caution against taking data from India at face value. Estimates put the amount of COVID-19 infections in india at around 80 times the "official" count.

See - https://www.deccanchronicle.com/nation/current-affairs/12092...

Further, there is a persistent myth among many from developing countries that constant exposure to unhygienic conditions improves one's "immunity". This has some truth for allergies but not for a disease that is quite literally new.

Finally, i would not go by India's death figures. Countries like India and China have every reason to hide the true number of deaths caused by COVID-19.

There is a massive difference between China and India in terms of information flow. India is very chaotic regarding centralized data control and it would be super hard to consistently fudge/ hide the death rates for this long.

many of the dead in india aren't tested for COVID. Who's to say what the accurate number of COVID deaths.

More info - https://www.nature.com/articles/d41586-020-01865-w

Remember also that India is the only country in the world to not acknowledge community transmission. There's little to no contact tracing happening.

Regardless of information flow, India's COVID numbers are likely off by orders of magnitude.

You don't need malice to get false deaths counts.

Immunity is complex. Our immune systems are very complex. We've measured immunity based on antibodies for decades, but what if that's not the entire picture?

Our immune systems have Memory T-cells, a Complement Protein system, and several other components to both our adaptive and inane immune systems. The sheer complexity of it is due to millions of years of bizarre evolutionary warfare. Just look at this video that simplifies the Complement system: https://www.youtube.com/watch?v=BSypUV6QUNw .. it's still insanely complex even when simplified.

The majority of vaccines we have today are not byproducts of careful genetic manipulation or breeding. They're other viruses that are similar to the one we want to protect against, but less harmful in humans, or they're inactivity through heat or chemical treatment. The first vaccine was based on horse/cowpox 185 years ago by Jenner, and was tested on random people because thousands were going blind or dying and we didn't have the ethical standards on human testing we do today.

They produce antibodies, yes, but there could be hundreds of other interactions there that help different parts of our immune systems build memory. Our immune system is like looking at millions of years of bad software engineering; microservices that were randomly put together by monkeys on typewriters that randomly got things right here and there along the way.

SARS1 and MERS vaccines resulted in some subjects developing Immunopathic responses or Immune Enhancement syndrome. These new vaccines that are being produced seem focused on just generating antibodies using synthetic proteins, which might be missing a bigger and more complex set of interactions that we don't realize is happening with inactivated viruses as vaccines.

This is why I wish we'd done more basic research on the immune system long ago. Maybe if we'd invested more time and money into a vaccine for HIV/AIDS, a disease which attacks the immune system directly, we'd realize we need to do this basic research on how our immune system works in order to even begin to understand a pandemic and our response to it. But at least I have hope we're getting it now so when something worse comes along we'll be more ready for it.

According to sero survey done in India 40% population had Corona anti bodies in May.

By that logic, herd immunity must be kicking in right?

The rules of nature mean that many people will be immune to corona or would have little to no symptoms.

Those with co morbidities will face issues unless a vaccine or a medicine comes out.

The only major issue is that cities are running out of beds. In my town hospitals have a 15day waiting and people are literally at home despite having symptoms

> The only major issue is that cities are running out of beds. In my town hospitals have a 15day waiting and people are literally at home despite having symptoms

Hello could you post some articles about this?

I have yet to see an article about people being turned away from hospitals and dying anywhere in the world.

https://www.deccanherald.com/city/top-bengaluru-stories/no-b...

If there were components of commonly consumed foods that turned about to be inhibitory to the virus' action (infecticity or replication), and these foods were unevenly consumed across the population, would this read out to an epidemiologist looking from a birds-eye view similarly to "immunity"?

The thing is that Rn depends on the people behavior very strongly, and what are precise behavioral characteristics increasing the spread are still unknown. The level necessary to achieve her immunity may be like 60% for one nation, but be 25% for some other. Small mutations may also matter.

This is consistent with what Karl Friston said in May (https://www.theguardian.com/world/2020/may/31/covid-19-exper...):

>For example, it looks as if the low German fatality rate is not due to their superior testing capacity, but rather to the fact that the average German is less likely to get infected and die than the average Brit. Why? There are various possible explanations, but one that looks increasingly likely is that Germany has more immunological “dark matter” — people who are impervious to infection, perhaps because they are geographically isolated or have some kind of natural resistance. This is like dark matter in the universe: We can’t see it, but we know it must be there to account for what we can see.

Physics is especially a poor domain to pick an analogy from at the moment. But if we can borrow from that whole religious domain I think the following is more apt.

Maybe the people of Germany have an invisible halo protecting them from bad woo woo from Wuhan.

>Maybe the people of Germany have an invisible halo protecting them from bad woo woo

Yes, it's called Angela Merkel. The numbers are difficult ro read but it looks like countries with female leaders have faired better than the rest.

>perhaps because they are geographically isolated

Germany has open borders with all its neighbours and freedom of movement. There is a lot of migration, in no way could they be described as an isolated community.

Why is this article so filled with question-marks? The opinions and anecdotes attributed to various names from around the world do not seem to form a coherent thesis nor address the headline.

I'm not even clear whether Betteridge's Law applies. The answer seems to be "maybe?".

https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headline...

annecdata: My family physician in small town in India has treated 70 covid patient. 55 were totally asymptomatic.

> 55 were totally asymptomatic

What treatment were they given?

Did all 70 test positive?

Thanks for posting. It lends credence to collecting more data from everyone to better determine T-cell reactivity to a number of pathogens (virus, bacteria, etc) and then let the patients own their data with the freedom/incentive to share that data for research and education. I prefer trying to gather data to identify levels of pre-existing immunities and who is higher risk. The higher risk people could opt for an immune hammer (vaccine).

Agree with your position on this, your take sounds very sensible. I wondered at the start of this if some of the larger DNA databases would be mapped and analysed to look for markers for this exact sort of thing. ( 23andme, DOD, ancestry )

Vaccine/Treatment should activate Tcells + Bcells + IgM + IgG in Immune system to kill the Virus

https://en.wikipedia.org/wiki/Antibody#/media/File:Antibody_...

Can someone give an educated tl:dr; of all the comments, please? :-)

tl;dr

People are overinvested in the opinions they held in March, and will find evidence to support what they believed then.

On one side, we have the cohort of people who see this as literally the worst thing ever and we will all die. And you hate children and humanity if you want to eat at a restaurant.

On the other side, you have the crowd who sees this as a moderate case of the sniffles and society is overreacting due to the fact that the news media hyped this so aggressively

There is a very, very small minority of people who see it as squarely in the middle, a scary disease that we should protect people from, but with a more nuanced approach than lockdowns.

Perfect :)

> Could pre-existing immunity be more protective than future vaccines? Without studying the question, we won’t know.

TLDR!

It's a moot point. People either have pre-existing immunity or not.

Unless there's a cheap way of checking (read, cheaper and easier than vaccinating), there's no point in worrying about it (for the purposes of individual protection).

> At least six studies have reported T cell reactivity against SARS-CoV-2 in 20% to 50% of people with no known exposure to the virus.5678910

I suppose if the vaccine trial studies going on now return with anything more than half the infections of the control group (however they want to measure it), we'll have our answer.

Betteridge's law of headlines seems to apply. It's a mistake to assume that public policies, such as lockdowns, are the primary thing that changes human behavior, when mobility data has shown similar patterns in different places regardless of public policy. Natural social distancing, due to fear, by itself will change the replication number, especially since covid spread seems to be driven primarily by superspreading events among the most risky activities.

I'm glad people are researching all the possibilities, but spreading minor hypotheses like this around social media brings out the worst of armchair epidemiology.

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