[phantom0308]

Why would any country want herd immunity from infection when nearly every developed country has demonstrated the virus can be contained without such a large loss of life? It's not as if the specter of maxed out hospitals on the news for months on end is going to help the economy.

[duxup]

>the virus can be contained without such a large loss of life?

Generally speaking:

But then you have to keep containing it right?

There's not a magical end of containing unless the virus just goes away / a vaccine is available ... that doesn't seem to be a thing yet.

I'm not all for just letting the chips fall where they may, but success at preventing exposure to your population vs heard immunity means the folks who haven't been exposed have to keep avoiding it.

[toast0]

> But then you have to keep containing it right?

If you don't have herd immunity, then you need to be continually surveilling for it, and when it's present, switch to containment.

Containment is easier when the number of cases is small though. If you get a handful of cases, contact trace and make general advisory news releases. If you get more than 20 cases, ask people to wear masks. If it gets worse, then you have to take bigger steps.

[intotheabyss]

A lot of assumptions here. Immunity may not even be long lasting. I live in a country where we've largely stopped community transmission, and now we can open back up with masks for all to keep it that way until we all get vaccinated next year.

America's strategy (or lack thereof) is simply negligence.

[__blockcipher__]

Please stop repeating the “there might not be long term immunity” meme. It is unfounded and contradicts decades of established immunological principles.

Memory T-Cell reactivity to SARS-1 has been shown to persist across decades. The latest study showed strong activity after 17+ years.

SARS-2 is incredibly structurally similar to SARS-1.

Even if we pretend t-cells don’t exist, immunological memory is a thing. Once circulating antibodies have completely faded after months, there still remain memory b cells which persist across decades and will ramp up antibody production all over again when exposed to SARS-CoV-2. Therefore the subsequent infection is addressed more quickly and more powerfully, leading to lower peak viral load and therefore theoretically lowered transmissibility and vastly improved individual outcomes.

So if we pretend half the immune system doesn’t exist, then you can get reinfected months later but you will spread way less and not be at any significant personal risk of bad outcome.

Herd immunity works. It’s a natural phenomenon that has been unjustifiably demonized.

[raphlinus]

If herd immunity works, then what is your explanation for the fact that alpha and beta coronaviruses such as 229E, NL63, OC43, and HKU1 (responsible for many occurrences of the common cold) are in continuous circulation?

[__blockcipher__]

Great question. Reaching herd immunity does not cause a virus to stop circulating. It just stops it from spreading exponentially. That’s a common misconception.

What you are referring to is eradication, which has only ever been performed twice. SARS-2 is functionally impossible to eradicate due to its zoonotic origin and incredible spread.

Even with herd immunity SARS-2 is here to stay. That’s not a problem though, even if we could so something about it. Why? Because SARS-2 kills the very old but spares the very young. Therefore once it has passed through the current population, the set of SARS-CoV-2-naive individuals becomes dominated by new entrants to the world, meaning babies/toddlers, the same group that does not die to COVID-19 in any real numbers. Therefore unlike Influenza, recurring deaths from COVID-19 will be incredibly low in subsequent years.

[raphlinus]

As long as we're tossing around citations to the scientific literature which supposedly support our arguments, here's one I'm sure you will enjoy: https://www.medrxiv.org/content/10.1101/2020.05.11.20086439v...

[intotheabyss]

I never said anything about herd immunity, all I've said is that immunity may not be long lasting.

Basing an entire countries policies around a supposition that herd immunity is practical is, in my opinion, negligence. It's only practical for diseases that don't kill 0.5-1% of the infected population.

It's been proven that lockdowns and slow reopenings work to limit spread, followed by contact tracing clusters to prevent reemergence until community vaccination programs.

Americans are just bitter that their governments are totally inept.

[__blockcipher__]

2.8 million people die in the US every year. That's 1% of the actual population.

What is it about SARS-2 that makes it so that a few hundred thousand dead is impractical and negligent?

(BTW, the hidden argument of yours here is that we can successfully avoid that mortality by practicing containment which I dispute)

[intotheabyss]

Well I live in a country where we've contained the virus and far less than 0.25% of the population has contracted it, so you're just wrong. Maybe America can't contain, but they are the outlier in this pandemic due to their poor leadership and negligence.

[duxup]

I duno man the 'immunity may not even be long lasting' could be true but bringing that up seems like a weird sort of pseudo assumption too...

[intotheabyss]

No, it's a matter of assessing risk. Why would you risk infecting your entire population with a novel virus that kills on the order of 1% of all infected, when you can do shutdowns and perform slow reopenings to limit spread below 5% of the population until vaccination?

We should be assuming that immunity doens't last long and basing all policies on that assumption until proven otherwise.

[duxup]

I think you're pretty far off from what I was talking.

I wasn't encouraging infecting everyone intentionally.

I was noting the ongoing scale of effort required to protect everyone you keep a large % of the population unexposed.

>We should be assuming that immunity doens't last long and basing all policies on that assumption until proven otherwise.

I don't think that assumption makes sense at all with modern medical science.

[lambdaba]

I know it certainly appears like a suboptimal strategy, but it assumes that the measures did indeed do what they were expected, that's contentious (we can discuss why, but I think it's obvious).

In a risk-benefit analysis, it leaves future (speculative) advances in treatment VS acquiring herd immunity as quickly as possible and with minimal actual damage, for this it makes sense to maximize exposure for the less at risk.

Also, the summer is a better season to get infected, at least because of generally better immune system function (because of better vitamin d status).

[__blockcipher__]

Not just Vitamin D, but to a lesser extent nitric oxide as well.

Anyway to state your excellent point in a different way: “contain until vaccine” is a strategy based around a temporally unbounded future event. When has it ever made sense to bet the farm on a highly uncertain future event?

This world would be so much better off if we never knew that SARS-2 existed and therefore did not engage in any artificial suppression of natural transmission.

[tenuousemphasis]

Yeah much better for hospital ICUs to be overrun with patients across the entire world all at once. Great thinking.

[__blockcipher__]

Hospitals/ICUs being overrun in the United States is not realistic. I'm not equipped to discuss the medical capacity of other countries, but Sweden did fine.

[MereInterest]

Exactly. Absent a vaccine, herd immunity is the failure condition that occurs when a virus has infected as many people as it can within a population. It is the default baseline against which all interventions should be compared.

[claudeganon]

If immunity to the disease is not long-lasting (> 3 months), herd immunity is likely impossible. There are plenty of viruses that can reinfect people who have recovered from them (Coronaviruses being a common example of these) for which we have no herd immunity.

[abainbridge]

Is there any evidence you can re-contract Covid-19? If not, I'd fall back to the following argument: Some health care workers have been exposed regularly for six months by now. It'd be very news worthy if someone was confirmed to be re-infected. Given I haven't seen that news, I think I can conclude that immunity lasts at least six months in working age people.

Also, if I understand correctly, it has recently been shown that people who were infected with SARS 17 years ago still have memory T cells for SARS. (And, I think SARS is one of the viruses most closely related to Covid-19, and therefore there's reason to expect a long immunity period for it too).

"Memory T cells induced by previous pathogens can shape the susceptibility to, and clinical severity of, subsequent infections. <snip> We then showed that SARS-recovered patients (n=23) still possess long-lasting memory T cells reactive to SARS-NP 17 years after the 2003 outbreak." - from https://www.nature.com/articles/s41586-020-2550-z

[claudeganon]

There’s initial evidence of reinfection and limited immunity that are under further investigation:

https://www.vox.com/2020/7/12/21321653/getting-covid-19-twic...

https://www.theguardian.com/world/2020/jul/12/immunity-to-co...

[__blockcipher__]

There is no credible evidence of re-infection. The isolated cases can be explained away in a bayesian sense by PCR false positives or false negatives. It’s the usual base rate neglect fallacy.

The idea of reinfection contradicts decades of well established immunological principles. It also ignores the fact that we have a close relative of SARS-2 to study. That relative is SARS-1 and we have detected strong t cell activation after 17+ years. Therefore immunity is enduring and long lasting.

SARS-2 is substantially structurally similar to SARS-1.

Alternatively, take a statistical argument. There have been millions of cases around the world. SARS-2 is highly infectious for those who are susceptible. Therefore we would have thousands if not more well-documented, inarguable cases of reinfection. We don’t have those. All we have is a bunch of articles from heavily biased sources like Vox that have a vested interest in pushing the “doomer” narrative.

Why haven’t we seen widespread reinfection if it is truly possible?

[claudeganon]

As I pointed out downthread, there's a Kings College study under review that says antibodies seems to wane rapidly:

https://www.sfchronicle.com/health/article/With-coronavirus-...

https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v....

Likewise, asymptomatic cases appear to have limited immune duration and development:

https://www.jci.org/articles/view/138759#ABS

And meaningful immunity might depend on how much of the virus one is exposed to:

https://www.nature.com/articles/s41591-020-0965-6

If this research holds up, we'll have your well documented cases in probably 3-6 months. Frontline doctors, outside the one cited in the Vox article, are already insisting its true.

[js2]

Meta: your comments on this thread imply a degree of certainty that isn't justified by the evidence as I understand it. I am just a lay person here, but that's my impression as someone who has done a lot of reading.

As far as coronaviruses go, there are four mild human coronaviruses that are responsible for about 15% of common colds and for which humans do not develop any long lasting immunity.

There are also the three severe human coronaviruses: MERS, SARS-CoV, and SARS-CoV-2. AFAIU, long-lasting immunity to these is not well understood.

I do not understand how you can make such an authoritative statement about re-infection risk based on the limited data we have about SARS-CoV-2. Here's what immunologists have to say:

> In summary, progress since January 2020 has been impressive, but there is still so much more to learn. Are T cells protective and if so which are the key antigens and and cytokine effector programs to focus on? Are all T cell responses beneficial, or are some contributory to immunopathology and to be avoided? If it is indeed the case that antibodies are transient and T cell memory is more durable (though, how durable?), what can we learn about anomalies of T follicular helper-B cell interactions in germinal centers? In the short to medium term, we need to ensure that all of this T cell toolkit and knowledge is brought to bear on robust, comparative evaluation of the different vaccine platforms, their immunogenicity, efficacy and safety. Entering the next part of the battle, there are many thousands of people suffering the chronic aftermath of infection posed by chronic, so-called ‘long-COVID’ cases, characterized by diverse symptoms including fatigue, joint pain and dyspnea (19). A more detailed understanding of the T cell immunology will be valuable in deciphering this pathogenesis.

https://immunology.sciencemag.org/content/5/49/eabd6160.full

What I read there is a lot of "we're not sure yet."

[gridlockd]

Immunity isn't a binary, neither is herd immunity. While there are reports of reinfection, those cases are quite rare.

Even a modest degree of immunity can significantly lower spread. In France, Spain, Germany, you still have hundreds of cases every day, but they don't grow to thousands of cases anymore.

[claudeganon]

> While there are reports of reinfection, those cases are quite rare.

The disease hasn’t been around long enough to make this claim.

> Even a modest degree of immunity can significantly lower spread. In France, Spain, Germany, you still have hundreds of cases every day, but they don't grow to thousands of cases anymore.

This is true, but depends on the duration of immunity and a more uniform global response (or very tight border and quarantine adherence). Ongoing, sporadic COVID crises would still be pretty disruptive unless we have highly effective therapeutics.

[tripletao]

Sweden has roughly 80k confirmed coronavirus cases in 10M people. Assuming equal probability of first and second infection (which I believe undercounts second infections, since some people have more opportunity for exposure than others due to their jobs and lifestyles), and assuming equal probability of first and second detection (which again I believe undercounts), we should have something around 10M*(80k/10M)^2 = 640 confirmed reinfections.

So where are they? Are you claiming that these hundreds of confirmed reinfections simply haven't been reported? Note that the number of actual reinfections would be orders of magnitude higher; the calculation above already assumes underascertainment by a factor of ~100x. You can redo this math in any moderately hard-hit region, though I chose Sweden here because their rate of infections vs. time has been more constant (eliminating the possibility that all the infections happened in a brief early peak, after which everyone acted more carefully so there's no longer any opportunity for reinfection). I'm not saying that reinfection is impossible, just that so far, if it exists, it's very rare.

And please don't cite the Vox article. In normal times, it would be criticized as "science by press release" or worse, a single anecdotal case written up as definitive for the popular press, with no case history and no publication to review. Maybe the author's patient really did get reinfected and it's common (but that seems vanishingly unlikely to me per above), or maybe the patient was reinfected but it's rare like getting chickenpox twice, or maybe the patient just had one long infection and tested false-negative (which is very common generally) in the middle. But since the author has disclosed nothing but the shocking headline result, we can't know.

So I believe you are sowing public panic without evidence. While it is impossible to directly demonstrate that immunity for a disease discovered X months ago lasts longer than X months, it is reasonable to expect that in this case. Maybe you think that at worst, if you're wrong, then you're telling a noble lie--but the public health authorities who said masks don't work (remember that?) did too, and look how that ended up. I can easily imagine Trump on television a year from now explaining that because people got reinfected, the vaccine is obviously a scam.

Abandoning the truth in favor of a perceived noble goal has unpredictable but generally bad effects, and I wish people would stop. Or if you actually believe what you're writing, I'm not sure what to say--please read the scientific literature (and not the popular media, which has been horrible in all directions), dust off your high school biology, and make your best assessment based on that. I think you'll find that while the coronavirus is a very serious problem, it's not the near-apocalyptic one that your comments seem to imply.

[claudeganon]

There's a Kings College study under review that says the same thing. Antibodies seem to wane rapidly:

https://www.sfchronicle.com/health/article/With-coronavirus-...

https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v...

Likewise, asymptomatic cases appear to have limited immune duration and development:

https://www.jci.org/articles/view/138759#ABS

And meaningful immunity might depend on how much of the virus one is exposed to:

https://www.nature.com/articles/s41591-020-0965-6

I linked to the Vox article because it covers a lot of bases in disputing the spurious narratives that have circulated in places like the US, where the disease is out of control, pandemic response is poor, and various forms of denialism are used to excuse all of this. I don't think its an apocalyptic scenario for humanity writ large, but certainly a dangerous one for many countries, especially if an ongoing, effective public health response is required.

>While it is impossible to directly demonstrate that immunity for a disease discovered X months ago lasts longer than X months, it is reasonable to expect that in this case.

Instead of attributing motives to other people, perhaps interrogate your own need to insist on statements like this, absent any evidence, as well as the tone of your broader rebuttal. I have no intention of sowing panic or engaging in "noble lies," but nor will I embrace evidence-free narratives to soothe myself or others.

If the US intervened early or effectively with measures like those in Taiwan or South Korea, we would likely have the situation under control. It's still possible that we could do this and I hope that we do.

[ppod]

Cases are low and falling in New York, Sweden, London, Italy, Spain, despite varying and loosening social distancing measures. How do you explain that? Those places already have herd immunity. Serotesting for antibodies misses t-cell immunity and other forms of resistance, and variation in spreading patterns makes the herd immunity threshold lower than we thought. This is the only plausible explanation and nobody wants to admit it.

[jschwartzi]

Look, what you are saying makes sense until you say "This is the only plausible explanation" at which point I get lost. Just because you can't imagine other explanations doesn't mean that there aren't any. And this also presupposes that there are no hazards to anyone in that case. The fact is this disease remains very dangerous for a lot of people. So while it's plausible that we will have herd immunity sooner rather than later, it also misses the point which is that it's very dangerous to get infected with this virus.

[ppod]

Yes, I admit that the part where I said there were no hazards and that it was safe to get infected with the virus was wrong.

[dragonwriter]

> Those places already have herd immunity.

No, they don't, or they wouldn't have new cases, even without even somewhat looser mandatory controls than other places. What they have is some degree of immunity in the population (not herd immunity) plus (in some subset of those places) some degree of contact tracing backed by targeted mandatory, or at least voluntary, quarantines/isolation of the exposed, and (in large part because of the intense impacts each has had) voluntary general distancing.

[ppod]

You sound very confident. There are some epidemiologists at the University of Oxford who disagree with your definitions.

https://www.medrxiv.org/content/10.1101/2020.07.15.20154294v...

[gridlockd]

> No, they don't, or they wouldn't have new cases, even without even somewhat looser mandatory controls than other places.

That's not what herd immunity means.

The Herd immunity threshold is attained when the R factor drops below 1, assuming otherwise uninhibited spread. The threshold for herd immunity for COVID-19 has been estimated at 50-80%, but that is assuming an R0 that is likely overestimated.

Given that spread is still mitigated by certain interventions, and since we don't know the impact of those interventions on R, nor do we know R0, we don't know if we have herd immunity. However, we do have R below one in many European countries.

[tripletao]

Herd immunity isn't a binary threshold after which zero cases occur. Even in a first-order homogeneous and well-mixed SIR model, you may asymptotically approach 1 - 1/R0 of the population infected without ever getting there. If you do cross that threshold ("overshoot"), then the case count starts to drop, but new people still get infected and die on the downslope. The only case where a disease will naturally burn itself out abruptly is if there was massive overshoot, which would be bad, because it means yet more people died than necessary for natural herd immunity.

And for real some people have many more contacts than others (nurses, police, etc.). They get infected first, with disproportionate harm, but then become immune first with disproportionate benefit. That heterogeneity means 1 - 1/R0 is potentially a significant overestimate of the share of the population that needs to get infected for herd immunity, but there have been very limited efforts to quantify that so far.

It seems like some people believe natural herd immunity (from recovered patients) could work like vaccination does, to effectively eradicate the disease? That's probably false--the most likely natural endgame would be that the coronavirus becomes endemic, always present with some low incidence, with continuing mortality that's very low (because the incidence is low, and because older people probably benefit from immunity from when they were younger and the IFR for young people is <1/100 of older people's) but nonzero.

Finally, herd immunity and interventions (social distancing, masks, etc.) work together. It's possible (and likely I believe) that in hard-hit areas that now show R ~ 1, this is due to the product of both factors, and that either relaxing to their previous lifestyle or applying the same interventions in a naive (100% susceptible) population would show R > 1.

[notahacker]

Cases are lower still or zero in many other places with far too few cases to have achieved herd immunity. The only plausible explanation is that containment measures have some effect.

[zaroth]

Every increase in the percentage of people with immunity reduces R0. At some point, even absent any other measures, the R0 would be below 1 just due to the number of people that are immune; herd immunity.

But in any case, the immunity level of the population reduces the need for other measures in order to stay below an R0 of 1.

There’s a massive spectrum of efficacy in the dozens of different suppression or containment policies that can be applied, combined with demographics and geography of the location being studied.

But in any case, the immunity level of the population is a downward force on R0 that, for example, will naturally keep daily cases lower in New York vs. Florida regardless of policy.

[ppod]

https://www.medrxiv.org/content/10.1101/2020.07.15.20154294v...

The case rate has dropped faster as the restrictions have eased.

[notahacker]

I think you're confusing cause and effect here...