> 1. The true IFR is hard to estimate at this point, but looks to be around 1%. This is a very difficult question to answer with the data we have and all the limitations.

An IFR of 1% seems too high. This doesn't seem to line up with data from the Diamond Princess (~1% IFR in a population biased towards elderly). We can also look as a lower bound at the Theodore Roosevelt (the navy ship), which had I believe 840 positives, 4 hospitalizations, 1 death (https://www.sandiegouniontribune.com/news/military/story/202...), and this is a population heavily biased towards the young and fit thus why it's a nice lower bound.

> 2. There is little evidence that we can reach herd immunity levels of infection with a Coronavirus like SARS-CoV-2 as both the unconstrained R0 is too high and the immunity too short lived.

The unconstrained R0 doesn't mean we can't reach immunity, it just means that almost every single person needs to get it, which to me still seems preferable to years-long lockdown.

But the more interesting point of yours is the part about short-lived immunity. I'm going to copy-paste a portion of https://news.ycombinator.com/item?id=23025880 to avoid repeating myself too much:

I think of immunity simplistically as two components:

(1) The presence of actively circulating antibodies in the bloodstream. This is what the (oddly controversial) serology studies are measuring. It is thought that having a significant quantity of these antibodies prevents infection - i.e., what most people envision when they talk about immunity.

(2) Even after the antibodies have faded, there are still Memory B Cells, which lay dormant up to decades, waiting for exposure to the characteristic antigen (in this case, an antigen telling them that they have encountered SARS-CoV-2), at which point they resume and rapidly scale up production of antibodies.

The thinking here is that reinfection is likely possible after a sufficient length of time - whether that's a couple months or a couple years isn't yet known - but when you do get infected, your immune system will respond sooner, more strongly, and thus you will achieve a far lower peak viral load meaning a less serious infection with reduced transmissibility.

So in short, I'd like to see what makes you think the reinfection immunity window is short, but regardless of the window length, we can hopefully agree that the immunological memory cells will stick around for a while.

> 3. The IFR has a threshold where it dramatically increases when the number of new cases overwhelms the hospital capacity. We have seen this to a certain extend in Wuhan, Northern Italy and NYC.

Agreed. My only caveat is this effect is probably not _as_ dramatic as it initially looked, but it is definitely dramatic.

> As treatments improves the IFR should fall. This mean if we can shift an infection to the future we should see less people die. Flattening the curve is more than just avoiding overwhelming the hospital system, it is also about shift cases to a time when we have improved treatments.

Also agreed. I thought about paying lip service to this notion but decided to leave it out of the first draft. Basically my assumption (and it is an assumption) is that the treatments we discover will do a little bit but not a lot. So probably what we've learned thus far about proning, managing oxygen levels etc doesn't leave a ton of room for improvement without a miracle therapeutic. I think antivirals and other treatments will help a small amount but not nearly enough to justify postponing infection.

But yes, at this point I think we can say that in a scenario of successful full containment+vaccine, we would have less area under curve as far as the "overshoot" is concerned and also to a lesser extent the improvement in treatments.

> Sweden has shown that it doesn’t matter if you have an official lockdowns or not, most people will self isolate on their own. There is little extra economic damage from imposing official lockdown policies since all the damage is done by people avoiding infection on their own.

I have to strongly disagree with this. In fact I view this as a strong point in favor of "my" side: we can get the majority of the benefits of the lockdown without actually locking down.

The magnitude of economic damage is much more than just the demand dropoff. We've forced closures of businesses that actually would have been able to stay open. And particularly small businesses which are not well equipped to weather systemic shocks.

But to be clear, I absolutely agree that even without a lockdown we would see very sizeable demand drop-off and thus there would still be some sizeable amount of furloughing, layoffs etc.

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Thanks so much for the points. In particular I'd really like to hear more from you about (2), since that is the point I disagree most with, and after that, point (1). 3-5 I have very few objections as discussed