[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.

[tripletao]

I appreciate the reply, and I agree that the concentration of antibodies in the blood has been observed to drop with time. That's relatively common in many diseases though, and doesn't mean that the patients no longer have any useful immunity. The test thresholds were set for best (but still imperfect) discrimination between known positives (mostly severe cases) and known negatives, and there's no specific reason to believe they predict when a recovered patient becomes susceptible again. They're also testing for IgG, when we know that T cell and IgA immunity are important. One of your papers mentioned IgM, which is expected to drop quickly to undetectable levels while the patients retain immunity (not to say you suggested otherwise, of course).

I also agree that whatever immunity patients get after a mild or asymptomatic case is likely to be weaker than after a severe case. That's one case where my calculation above could be wrong--if there are many reinfections but the first or second case is always very mild, we might be much more likely to miss those. That would still be good news for the patients, though bad news for the overall population if they're still comparably infectious.

Finally, even if a patient's immunity degrades to the point they no longer exhibit sterilizing immunity (i.e., the virus still replicates a little at first), in most diseases they won't get as sick as the first time. So even if the coronavirus becomes endemic (which seems relatively likely, since many countries will lack the resources to eradicate it even with a vaccine), I expect the cost in mortality from whatever reinfections do occur to be far lower than what we're seeing now. The opposite of that (antibody-dependent enhancement) does occur, and was a specific concern here because vaccine studies for the original SARS showed evidence of that. So far vaccine studies for SARS-CoV-2 do not, though.

I actually thought the SF Chronicle article wasn't terrible, more pessimistic in its conclusions and tone than I would be given the same evidence but with many of the points above. Their headline seems irresponsible to me though; even if durable sterilizing immunity were impossible, a vaccine that cut the IFR by a factor of ten would be tremendously valuable to the elderly. All that nuance is lost when people just say "reinfection is possible". I was probably too strong to say "sowing public panic", but I do believe your comments paint a falsely pessimistic picture of the current science, and that this false pessimism can be harmful later (e.g., by causing people not to seek a vaccine because of something they half-understood about immunity). Specifically, I also believe the absence of confirmed reinfections out of places like Sweden is strong evidence that immunity usually lasts >3 months. If you were claiming that reinfection might be common after a year, then I'd be much less sure (though I'd still guess probably not based on the original SARS).

In any case, I certainly agree that younger people shouldn't get themselves deliberately infected in search of whatever immunity that affords (though the death rate among young people is low enough that I doubt reinfection would change the calculus for anyone considering that either way). I also agree that the USA response has been terrible, and resulted in a lot of avoidable death--I'm not sure, but it seems possible to me that just with universal mask use and good hygiene (like in Japan), we could live otherwise normal life with negligible spread.

ETA: And here's a paper showing neutralizing antibodies for at least three months (the limit of the study, which they're continuing) in New York. It seems beyond any reasonable doubt to me that immunity lasts three months, and I believe you're simply wrong to question that. Longer gets more speculative, but I think it's quite likely.

https://www.medrxiv.org/content/10.1101/2020.07.14.20151126v...

[claudeganon]

I agree that the evidence suggests an at least 3 month immunity for symptomatic cases, but anything beyond that is up in the air and complicated by how asymptomatic cases relate to immunity. I'd personally get the vaccine if it had proven immunity or reduction in severity for just this amount of time, if only to benefit others at risk and prevent asymptomatic transmission. And certainly would never dissuade others from doing so.