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Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

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Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#101

Post by meowzero »

hammock wrote: post #18
umvi wrote: post #2

So, according to this paper 34.2-47.5% of US citizens need immunity before the pandemic can be declared over? So best case scenario we can achieve herd immunity with roughly 100M infections/recovered. USA is currently at ~8M infections/recovered, so that means we are roughly 8% of the way to herd immunity (best case). At the current rate of +50K infections per day, that's 20 days per 1M infections, so we need 20 days…

Well, we could get to 2MM faster if we opened everything up for the less-vulnerable populations (i.e. everyone under 50 without obesity or heart conditions) for whom the survival rate is above 99.99%. You might then be looking at 500k a day rather than 50k.

That is a good strategy. Unfortunately, ppl with survival rate above 99.99% might live with more vulnerable population. It'll be difficult to figure out how to effectively quarantine the more vulnerable population away from the less-vulnerable.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#102

Post by PaulDavisThe1st »

mikelward wrote: post #74
pbhjpbhj wrote: post #55

Earlier quoted context omitted.

FWIW they almost certainly didn't write on a cigarette package in this instance ;o) It's just the name of that type of maths because people used to use whatever small, available, piece of paper was around - so cigarette packs some time ago (you definitely could write on them with a ballpoint pen (ie un bic ). Getting tangential, napkins to me in the UK have always been cloth, and we have serviettes (a French word, me…

I can't decide whether to use the term cutlery (mainly UK) or silverware (mainly US). They're both inaccurate, especially when asking for plastic/disposable versions.

https://separatedbyacommonlanguage.blogspot.com/2008/09/stem...

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#103

Post by NationalPark »

oopsiforgot7 wrote: post #21
jupp0r wrote: post #15

Keep in mind that "herd immunity" isn't really immunity, it's the point at which Rt (the average number of people each infected person passes the infection on to) drops below 1.0 and the spread shrinks instead of growing. Rt is dependent on how people behave. When behavior changes, Rt can change as well. Each herd immunity level is thus dependent on health measures, which is why "reaching" herd immunity and then loos…

When non experts talk about herd immunity they mean herd immunity given no to minimal precautions. This is a well defined concept.

If that's an informal lay interpretation I don't think it can be well defined, by definition.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#104

Post by timr »

watwut wrote: post #42
jupp0r wrote: post #34

Earlier quoted context omitted.

> R0 is not a constant inherent to a virus strain. It's a contextual number, determined by population and behavior, population immunity and other factors. From Wikipedia: In epidemiology, the basic reproduction number, or basic reproductive number (sometimes called basic reproduction ratio or basic reproductive rate), denoted {\displaystyle R_{0}}R_{0} (pronounced R nought or R zero),[20] of an infection can be thoug…

> can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection Yeah, and that is contextual number, determined by population behavior and other factors. Yes, population immunity should not be on that list, but the population behavior, weatcher and what not are still influencing it a lot.

Population immunity has to be on the list: if the population has some level of immunity, it affects the observed R0. And we can't really measure immunity, other than in very crude ways (i.e. antibody tests for specific epitopes), so we can't control for it.

This isn't a political statement of any sort.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#105

Post by rednerrus »

hcknwscommenter wrote: post #85
jwlake wrote: post #62

Earlier quoted context omitted.

Source? 0-4 and 5-17 are definitely that high. The 18-45 demo is different, but there's a lot more heterogeneity in that population as well. https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm

I cannot fathom how your link could possibly support your contention that 0-4 and 5-17 are "definitely" a 99.99% survival rate (IFR of 0.01% or 1 fatality out of every 10,000 infections). I suspect you are misreading the table? Care to elaborate?

How about this one: https://www.nber.org/papers/w27597.pdf?

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#106

Post by orangecat »

matthewdgreen wrote: post #95
orangecat wrote: post #79

Earlier quoted context omitted.

For the record, FL lost 139 people yesterday 139 deaths were reported; those deaths actually occurred over the last several months. Which means we won't know how many actually died yesterday for a while, but it's likely well below 139. Jennifer Cabrera posts regular updates with dates of deaths, e.g. https://twitter.com/jhaskinscabrera/status/13139124858340884...

You make this out like I've picked on some rare outlier day, but the state has had multiple days in the past two weeks with even bigger death numbers. The 7-day average is a pretty substantial 85. If your point is that the drop since August has been more substantial, then I would need to know that the older, higher numbers were not also subject to the same delays. https://public.tableau.com/profile/peter.james.walker…

You make this out like I've picked on some rare outlier day

Sorry, I didn't mean to convey that impression. Florida has been regularly reporting daily death counts that include deaths from several months ago.

I would need to know that the older, higher numbers were not also subject to the same delays.

They were, in the other direction. If you look at the date-of-death chart in the thread I linked, you'll see that for a few weeks there were consistently over 200 actual deaths per day, while the reported 7-day average in your chart never reached 200. The delay means that the reported count will be lower than the actual count when deaths are rising, and higher than the actual count when deaths are falling.

And of course we can't be sure which of those categories we're in at any particular point in time; if deaths do start to increase again, it may not be noticeable in the reported numbers for several days. But based on the hospitalization trend I believe it's probable that the current reported numbers overstate the actual deaths.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#107

Post by Animats »

saalweachter wrote: post #93
Animats wrote: post #84

Whatever happened to large-scale antibody testing? You'd think that someone would be testing a few thousand random people each week to see how many people have been infected to date. That sort of thing was being done in the US back in April.[1][2] But it seems to have stopped. If you're going to talk about "herd immunity", you need that info to get anywhere. [1] https://www.medrxiv.org/content/10.1101/2020.04.14.2006…

There was a recent study of dialysis patients: https://www.thelancet.com/journals/lancet/article/PIIS0140-6... TLDR: "During the first wave of the COVID-19 pandemic, fewer than 10% of the US adult population formed antibodies against SARS-CoV-2, and fewer than 10% of those with antibodies were diagnosed."

That's for the month of July 2020, which is useful, but not enough. We need trend data for this.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#108

Post by ars »

matthewdgreen wrote: post #69
StevePerkins wrote: post #16

Earlier quoted context omitted.

I think the common perception on HN, Reddit, etc is that COVID spread in the U.S. is primary a matter of conservative people flouting its seriousness. I understand the satisfying appeal of that picture. However, I'm looking at my local health department's ZIP-code-by-ZIP-code infection map of the metro area. And it seems almost entirely correlated with poverty, not privilege. Infection spread seems mostly due to "ess…

I think the reason that HN, Reddit et al. have this impression is that state policies in conservative states are explicitly less restrictive than those in less conservative states. Florida just removed all stadium event attendance limits, for example. Within any given state there are all kinds of political beliefs and economic situations that may be more or less correlated with spread, but state governance is a very…

And yet New York and California, both states with primarily liberal policies, have more cases than anyone else.

It's pretty obvious to people watching that the impression was created by liberal media that just wants to bash conservatives.

A cursory check of the numbers shows that it has no basis in reality.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#109

Post by xadhominemx »

hammock wrote: post #75
mcguire wrote: post #64

Earlier quoted context omitted.

Are you seriously suggesting we lock over 110,000,000 people (34% of the population) in close quarantine for the duration? How do you plan to feed them? Get them medical care (be sure you don't overwhelm the system with the under 50s that get sick)? Keep them from rioting against their captors? What happens when you decide it's good enough and release them, and the residual infection sweeps through that population li…

>Are you seriously suggesting we lock over 110,000,000 people (34% of the population) in close quarantine for the duration? As opposed to 100% of the population? It sounds like an improvement to me. I'm suggesting relaxing restrictions for a part of the population, not increasing them.

Who is suggesting 100% of the population be under close quarantine? We haven’t seen anything like that since April.

Re: Updating Herd Immunity Models for the US: Implications for the Covid-19 Response

#110

Post by ars »

matthewdgreen wrote: post #97
School-Cotton wrote: post #90

Earlier quoted context omitted.

Is there any evidence that level of restriction correlates with severity of outbreaks, though?

I mean, this seems to be the basic understanding of every single epidemiologist and public health expert, and also correlates with everything we know about the physical mechanism of how COVID spreads.

To me it seems like a covid infection is inevitable. You can delay it, but if you look at the state-by-state figures: states that successfully delayed for a while eventually got hit, states that got hit did not get additional infections.

I get the idea of flatten the curve but states that already got hit hard don't really have any reason to impose additional restrictions they wouldn't do anything.

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