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...

Antibodies do wane, and they are supposed to. They generally don't last longer than a few months with SARS-[1,2].

Even though they wane, memory b cells persist, meaning subsequent infection is milder and theoretically less transmissible.

Additionally that reinfection potential only exists if you ignore t-cells. When you factor in t-cells, it simply does not happen.

We're in July 2020. SARS-2 existed since some point in 2019, probably midway through. Granted we couldn't detect reinfection until the whole globe had been freaking out about it, so let's start our clock from January 2020.

It's been 6 months and we don't have dozens of well-documented, credible reinfections?

No, such one-off supposed reinfections are much more explainable from a bayesian perspective of either false positives or false negatives of PCR.

Find me someone who is not immunocompromised, who is PCR-positive for SARS-2 and from whom viable SARS-2 is successfully cultured, then show them fighting off the infection and being PCR-negative and symptom-free for weeks, then show me them being PCR-positive again with viable SARS-2 cultured from their body. That's the standard.

20 examples of that and reinfection definitely happens. Until then, our priors are that we should assume it does not.

Such fears are just used to argue against herd immunity, which has been made into a "dirty word" (phrase). Herd immunity is a natural phenomenom, arguing "against" it is like arguing against natural selection in my book. (The analogy is not perfect but I hope you see the point. I'm tired of being called callous for saying "hey let's not fuck with the normal population immunity dynamics that we've used for every other highly infectious virus in existence")

---

BTW, I can't find the study but they have tested reinfection in primates and showed them unable to get reinfected

Of course there's uncertainty, but the idea of re-infection contradicts decades of established immunological principles.

At a minimum, we can agree that in the event of re-infection, the subsequent infection will hit a lower peak viral load and therefore theoretically a much milder outcome with reduced transmissibility, right? This is called immunological memory and arises due to memory b cells and memory t cells which persist across decades.

Anyway, please see https://www.nature.com/articles/s41586-020-2550-z

It establishes that those exposed to SARS-1, which structurally and functionally is incredibly similar to SARS-2 and thus is our best model of how to think about SARS-2, have long-lasting immunity. Their t-cells not only react to SARS-1 after 17 years, they also have immunity to SARS-2, which is a testament to how similar they are structurally speaking.

Additionally exposure to those common cold human coronaviruses you mentioned almost certainly confers immunity to SARS-2 based off that same paper. We're still hashing out the details, of course.

Immunology is incredibly complex and there is still plenty to learn about as far as the exact specifics of what unfolds here, yes. But we should assume reinfection isn't possible, because:

- It doesn't happen in SARS-1 which is by far the best model we have

- If it did happen, given the MILLIONS of cases of COVID-19 worldwide, we would have seen THOUSANDS of rigorously documented examples of the phenomenom happening

- Those arguing for reinfection tend to not make any mention of immunological memory

- Those arguing for reinfection do so to in an attempt to scare us into staying locked down until "the vaccine", which I am opposed to because I am opposed to any public health policy that banks on a future technological innovation that does not yet exist, particularly when I fear that the environment of irrational fear and anxiety and outright hysteria is going to be used to mandate vaccines, which is highly unethical under my moral framework

--

As far as me sounding over-certain, frankly it's cognitive draining to be arguing against a horde of people whose priors have been completely screwed up by programming from a media that takes delight in knowingly lying to citizens, and even our trusted public health officials like Fauci don't have the courage or perhaps the desire to break out of the collective mass delusion we are all trapped in.

So yes, if I had infinite time and energy I agree, I could do a way better job of capturing uncertainty. I've written an 8000+ word writeup on COVID that does a much better job capturing the uncertainty, but it's very difficult to do without...writing 8000 words.

Also this doesn't justify it but I do feel the need to point out that those arguing for the "doom" scenario are even more egregiously overstating certainty, and tend to not be called out on their ridiculous statements. So that's why I tend to come into these threads guns blazing, with the predictable result of getting hammered by downvotes. C'est la vie.

See, they use general human coronaviruses as a model, instead of SARS-1, which is incredibly functionally and structurally similar to SARS-2.

Why would you willfully ignore the enormous research literature showing enduring immunity developing from SARS-1? Oh, right, because either you haven't read it or you don't like that it doesn't support your conclusions.

It's like, imagine we're discussing H1N1 reinfection, and we have a highly similar H1N0 which varies very slightly, and we know that doesn't lead to reinfection. But instead you look at a number of Influenza viruses in the same family but not nearly as similar.

Don't you see how ridiculous that is?

We obviously should use SARS-1 as a model for SARS-2.

Okay, but now your country can't let anyone into it without 2+ weeks quarantine. Similarly you need to be ready to "lockdown" (or whatever policy your country used) at any given moment if there's a flare-up.

Practicing containment is like leaving a forest full of extremely dry brush. It works great until the fire starts.

> That's not a catastrophic failure at all; early (unrealistic, but that didn't stop our policy leaders from using them) estimates were forecasting 2.2 million dead, that's Ferguson's paper with a .9% IFR and 82% of pop. getting infected.

Honestly we might as well stop the conversation here. A quarter of a million extra dead isn't a failure? Wow. You and I just don't have anywhere close to the same values.

Even if these strangers blithely brush past you, making no attempt to maintain social distancing? Sometimes they'll even come up from behind you, giving you no chance to avoid them.