Comment by tunesmith | Hacker News Reader

Comment by tunesmith | Hacker News Reader

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Sorry, can someone spell out how this might be good news? 21% is still a long way from herd immunity, and NYC's hospital system has been severely strained getting to this point. On top of that, the hospitalization rate still seems disproportionate to someone getting the flu - maybe it's five times as fatal, but it's > 5x the flu hospitalization rate. It's not like the virus has become less dangerous, we're just realizing how dangerous it has been, what with the impact we've already experienced.

Besides, generally if a virus is less fatal than previously expected, it means it's more contagious, meaning that much harder to get to herd immunity.

Good news would be things like: evidence the virus has mutated into something less severe; evidence of an anti-viral treatment that improves outcomes for everyone so it's not as big a deal to catch it; evidence that community spread has halted in an area and the boundaries are controlled so people in that area can feel secure they won't catch it; evidence of an impending vaccine.

Is this good news just because we're finally establishing that people have caught it once can't re-catch it for now? I guess I can see that as good news but that is so expected that it's more like it would be horrendously bad news if we found evidence that recovered people didn't have antibodies. But generally I don't really see what policy impact this has, other than identifying a pool of workers that can go work in meat-packing factories without fear of catching it again.

The only good news that I am getting out of this, is that NYC seems to have avoided the dreaded 3-5% fatality rate that was the presumed worse case scenario (massive community spread, overloaded healthcare system). But the lockdown likely helped a lot, and it seems like they are seeing around 1% IFR, so I am not sure this really changes anything. Our understanding of the disease and how to treat it may also be getting better, but it still seems like if we let this thing run wild through the population (as some people on here are proposing) local health care systems will collapse and we will have a IFR orders of magnitude higher than the flu.

And as you pointed out, if the study came back with an infection rate of 50%, I am not sure I would consider that good news either. That means it would be nearly impossible to isolate vulnerable populations. So while a 50% infection rate would mean the IFR is lower, it also means opening things back up and only isolating the vulnerable would not work to protect them.

If the infection rate were 50% we would be close to herd immunity (which I've read would require about 70% for this virus), so that would be better news in a sense.

Unfortunately 21% is a long way from 70%, and it's taken a massive amount of death to get to that point.

The herd gets substantial benefits long before you get to 70% or whatever rate for full herd immunity.

The spread starts to slow before that point. If you're walking around infected and 20% of the people you come in contact with cannot catch it from you, 20% less people are going to catch it, no matter how much you cough on them.

The R0 value impacts herd immunity %. So if NYC is already at 50%, then it means R0 is much higher than we thought, which means herd immunity would probably be as high as +90%. With numbers like that, not shutting down would result in the entire population getting infected in the span of a month or two.

The point I was trying to make, was that for the 'open back up' crowd, they are arguing that the IFR is similar to the flu, and only vulnerable populations are really impacted. So they say we should open up and just keep vulnerable population in lockdown. But they are ignoring the implications of the R0 value in their argument. i.e. if the IFR is really as low as they think (and consequently, the infected population is as high as they think), then nothing short of a total lockdown (or very aggressive testing and contract tracing) would stop vulnerable populations from getting infected.

Also, protecting the vulnerable sounds simple, but is incredibly difficult in practice.

> Sorry, can someone spell out how this might be good news?

It's good news because it strongly suggests that mortality is much less than previously suspected. There were numbers floating around from anywhere between 10% to 3% a few weeks back. A mortality rate < 1% is very good news because it means fewer people will die in the long run.

> mortality is much less than previously suspected

Mortality remains pretty much as suspected already two months ago:

“Based on these available analyses, current IFR estimates10,11,12 range from 0.3% to 1%. Without population-based serologic studies, it is not yet possible to know what proportion of the population has been infected with COVID-19.”

https://www.who.int/docs/default-source/coronaviruse/situati...

The princess cruise ship study also gave an IFR (for China) of 0.5%, and an early epidemiological modeling study put the symptomatic CFR at 1.4% which would imply 0.7% IFR assuming it's 50% symptomatic.

https://www.nature.com/articles/s41591-020-0822-7

https://www.medrxiv.org/content/10.1101/2020.03.05.20031773v...

0.5% to 1% has been the most plausible for at least a month, and this NYC study seems to exactly line up with that.

Two weeks after that the WHO released a widely cited report claiming a fatality rate of 3.4%.

“Globally, about 3.4% of reported COVID-19 cases have died. By comparison, seasonal flu generally kills far fewer than 1% of those infected.”

https://www.who.int/dg/speeches/detail/who-director-general-...

CFR will be higher than IFR due to undercounting infections.

Yes, and then almost the entire US press spun the 3.4% figure as the real WHO-confirmed fatality rate and sub-1% numbers as a Trumpian lie as part of a stupid, cynical, partisan attempt to get Trump. There's been a lot of that. (The UK press, meanwhile, happily quoted the 1% figure - if I remember rightly, some outlets like the Guardian with both UK-facing and US-facing sides pushed both narratives to different audiences at the same time.)

In reality, the WHO number was just confirmed deaths divided by confirmed cases, which was of course almost completely meaningless.

Mid single digit percentage mortality rates were the numbers for case fatality rate, not infection fatality rates. Infection fatality rates have consistently been around 1%.

This comment is entirely wrong. The mortality rates are right in line with what was expected with an IFR of > .5% unlike the Stanford study which was claiming something much lower.

I don't know if the hospitalisation rate is so out of whack vs the flu. It should be higher. But does 20% of the population catches the flu in a matter of weeks?

Much of the population gets a flu vaccine so would be tricky to compare.

My very point. It contaminates people at a slower pace, for that reason and cross immunity, higher R0, etc.

it is more like would the 20% population go to the hospital if they suspected they had the flu

if they did the hospitalizations would rise as well

one reason the hospitalizations are falling has less to do with the numbers of cases and more with doctors ability to better tell who might need it.

Every person who is infected that we don't know about lowers the estimated hospitalization and mortality rates and reduces the ability of the virus to spread (for as long as immunity lasts in the individual).

21% sounds much closer (eg. months) to herd immunity than previous estimates (eg. up to a decade).

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