Ryan since you have asked for comments here are some from me.
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.
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.
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.
4. 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.
5. 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.
My feeling is the author seems pretty open to criticism.
You should open a PR incorporating your reasoning into the document. Be respectful but make it better. I'd hope the best ideas would win out but then again the author has the authority to merge or not.
To the author maybe you should give one other person you respect whose opinion differs from yours the ability to merge PRS as well. Maybe...
> 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
That's the case fatality rate, not the infection fatality rate.
As you can see in your quote, I was talking about IFR. In general - and this is a theme of the writeup BTW - we should be looking at IFR and not CFR. With IFR we can reasonably extrapolate how many deaths we'll have before new infections halt, whereas CFR is borderline impossible to use because we'd need to know how many cases we would expect per infection. At which point, why not just calculate the IFR anyway, right?
> Adjusting for delay from confirmation-to-death, we estimated case and infection fatality ratios (CFR, IFR) for COVID-19 on the Diamond Princess ship as 2.3% (0.75%-5.3%) and 1.2% (0.38-2.7%). Comparing deaths onboard with expected deaths based on naive CFR estimates using China data, we estimate IFR and CFR in China to be 0.5% (95% CI: 0.2-1.2%) and 1.1% (95% CI: 0.3-2.4%) respectively.
That article is from early March. It’s May now, no need to estimate anymore. I agree that CFR is fairly useless. But if you test everyone, as was the case on the Diamond Princess, IFR = CFR.
1. Estimating the IFR is difficult because of difference in populations infected - in the end you need to make an estimate based on the best data possible. The Diamond Princess data was not biased towards the elderly as much it would appear as a large number of the positive case were in the crew who are younger. We also don’t know the true death rate as many cases were lost to follow up.
Even if the IFR turned out to be 0.5% in the end (I hope it is) this is still a lot of dead people.
2. Coronavirus are rather unusual for pathogens in that our immunity to them fades very quickly (less than a year on average) and you can get reinfected again. The question is if SARS-CoV-2 the same. We only have limited data so far, but if you have a look at figure 3 of this pre-print paper [0] you will see the antibody response has faded significantly 60 days post infection.
3. I think it was pretty dramatic in Wuhan, Northern Italy and NYC, but I guess this is one of personal opinion. What is certain is if the number of cases had doubled the system there would have broken down completely.
4. We seem to be in agreement.
5. The reports coming out of Sweden suggest that the economic damage there is just as bad as those countries that went into an official lockdown [1,2]. All Sweden seems to have accomplished is the killing of a large number of elderly Swedes.
Most people are not idiots and they won’t put themselves at risk of getting COVID-19 if they have a choice, but there are enough idiots that won’t self isolate to cause problems. If the economic difference of going into lockdown is the same as not, then why not help idiots not be idiots.
I don't have anything substantive for right now, but just wanted to say that I've gotten a lot of value out of your responses in this thread and really appreciate you taking the time to do so.
Excellent. This is the what makes HN so valuable (when it works) - bring together intelligent people in a forum where they can discuss a topic in a respectful way - the opposite of Twitter :)
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.
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.
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.
4. 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.
5. 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.
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