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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

#61

Post by mcguire »

StevePerkins wrote: post #16
HarryHirsch wrote: post #10

Earlier quoted context omitted.

We know that coronaplague spreads through superspreading events, person-to-person transmission is wildly variable, most people don't infect anyone, but some give it to a dozen. You'd like to know if people are wearing masks at church or if family get-togethers are now outdoors.

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…

Anecdotally, out here in the rural wilds of Alabama, most people seem to be wearing masks. I recently went into downtown Huntsville and no one was. Poverty and essential workers may be a significant component, but given the behavior of the young and affluent here, I don't think that is all of it.

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

#62

Post by jwlake »

hcknwscommenter wrote: post #58
hammock wrote: post #23

Earlier quoted context omitted.

Why the massive downvotes?

Because no demographic has been demonstrated to have a 99.99% survival rate?

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

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

#63

Post by vannevar »

nradov wrote: post #32

These models are fundamentally flawed in that they assume immunity or susceptibility are binary conditions. Based on recent research it appears a significant fraction of the population has at least limited immunity from prior exposure to other coronaviruses. They can still get infected but the immune system clears it more quickly and they tend to suffer fewer symptoms compared to immunologically naive patients. https…

I believe this model accounts for such individual response:

"Heterogeneity in contact structure and individual variation in infectivity, susceptibility, and resistance are key factors..." (emphasis added)

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

#64

Post by mcguire »

hammock wrote: post #23
hammock wrote: post #18

Earlier quoted context omitted.

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.

Why the massive downvotes?

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 like wildfire?

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

#65

Post by AstralStorm »

vannevar wrote: post #63
nradov wrote: post #32

These models are fundamentally flawed in that they assume immunity or susceptibility are binary conditions. Based on recent research it appears a significant fraction of the population has at least limited immunity from prior exposure to other coronaviruses. They can still get infected but the immune system clears it more quickly and they tend to suffer fewer symptoms compared to immunologically naive patients. https…

I believe this model accounts for such individual response: "Heterogeneity in contact structure and individual variation in infectivity, susceptibility, and resistance are key factors..." (emphasis added)

In general, that's one of those anomalous diffusion problems. Unfortunately, there are too many parameters to estimate without simplifying the model. So the reasonable solution is to take a maximum expected value of each and you can still be wrong.

Important data we do not know is chiefly how effective SARS aerosols are and at what range and time.

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

#66

Post by AstralStorm »

learc83 wrote: post #37
StevePerkins wrote: post #11

Earlier quoted context omitted.

Well, then add on the number of people who just don't get a test regardless. My child had a fever a few weeks ago, it was an ORDEAL finding a place to get him tested. You have to be quite motivated. If you're not sick enough to require hospitalization, and especially if you're un-insured and poor and don't want to pay a couple-hundred bucks out of pocket, then you'll probably just ride it out and never get tested. I'…

>My child had a fever a few weeks ago, it was an ORDEAL finding a place to get him tested. You have to be quite motivated. That's because the test won't change anything. If it's positive, they'll tell you to isolate your kid. If it's negative, there's a high enough false negative rate that you'll still need to basically treat them like they have COVID (stay home and isolate).

Incorrect. Not being treated early is likely a main factor between likelihood of medium to severe.vs no to mild symptoms, beyond immunity. And isolation of sick patient from viral reservoir (such as fomites and other asymptomatic sick) is known to be important too, as it changes the viral inoculum dose.

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

#67

Post by cmrdporcupine »

StevePerkins wrote: post #6
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…

> USA is currently at ~8M infections/recovered CONFIRMED cases. The total number of cases is probably 5-10x that. I live in the Deep South, and honestly I suspect that our curves have fallen simply due to a "limited" herd immunity effect (i.e. the groups of people most likely to catch COVID have already done so in large enough numbers). I certainly haven't observed any significant change in behaviors since the July p…

I have a hunch that in reality the south has had flattening curves because the super hot summer weather is over and people are no longer spending most of their days in air conditioned buildings and are spending more time outside.

And the opposite is now happening in the north (again). People come inside as the weather gets colder, and respiratory infections in general get far worse.

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

#68

Post by matthewdgreen »

StevePerkins wrote: post #6
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…

> USA is currently at ~8M infections/recovered CONFIRMED cases. The total number of cases is probably 5-10x that. I live in the Deep South, and honestly I suspect that our curves have fallen simply due to a "limited" herd immunity effect (i.e. the groups of people most likely to catch COVID have already done so in large enough numbers). I certainly haven't observed any significant change in behaviors since the July p…

> I certainly haven't observed any significant change in behaviors since the July peak, yet the numbers are falling like a rock regardless.

Picking FL as an example: deaths are down only about 50% since the peak in August (7-day averaged), and the numbers are surprisingly "sticky" (in the sense that they're not going down all that quickly.) For the record, FL lost 139 people yesterday; that's nearly the capacity of a 737.

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

#69

Post by matthewdgreen »

StevePerkins wrote: post #16
HarryHirsch wrote: post #10

Earlier quoted context omitted.

We know that coronaplague spreads through superspreading events, person-to-person transmission is wildly variable, most people don't infect anyone, but some give it to a dozen. You'd like to know if people are wearing masks at church or if family get-togethers are now outdoors.

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 big variable.

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

#70

Post by tzs »

e40 wrote: post #14
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…

I wonder if this also means that only 35% of us need a vaccination to declare it over. I had previously read 60-70% were needed and that 35% of Americans get a flu shot. That depressed me. EDIT: seriously, downvoting this comment? Can't imagine why and would like to know.

I don't understand why more people do not get flu shots, unless they have no medical insurance and cannot afford the cost.

It's not always effective, because they have to predict when they make it what strains of flu will be prevalent in the next flu season, and they don't always get that right, but in that case you are no worse off than if you had not gotten the vaccine. But when they do get it right, it can save you from getting the flu. That's certainly worth a few minutes getting it an a couple days with a sore arm.

With a COVID vaccine, I doubt it will get anywhere near the same fraction of takers as the flu vaccine.

1. The anti-vaccine crowd probably won't take it.

2. The "COVID is no worse than a mild flu" crowd probably won't take it. Even if they do, it won't be at a higher rate than they take the flu vaccine.

3. The "COVID is a hoax" crowd probably won't take it.

4. A lot of the people who believe COVID is real and serious will probably be turned off if the approval seems to have involved politicians forcing approval over the objection of scientists who say it is not ready yet. (Especially if those politicians have also been pushing the "no worse than a mild flu" narrative).

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