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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

#41

Post by war1025 »

seanalltogether wrote: post #7
zwischenzug wrote: post #5

Earlier quoted context omitted.

Actual infection count is probably far higher than 8M, isn't it? That's just number of positive tests.

I thought I remembered reading early on that icelandic testing was showing that 50% of all people infected there showed no symptoms. Then add on how many people show symptoms but its not severe enough to get tested.

> Then add on how many people show symptoms but its not severe enough to get tested.

Earlier this week we took my son in because:

1. Our neighbors have recently recovered from Coronavirus

2. Our son had a cold / fever around the same time lasting several days

3. He had several days of diarrhea after the cold symptoms subsided

I talked to my coworker whose wife is a doctor and he relayed the symptoms to her and she said it very well could be a mild coronavirus infection.

We weren't concerned for his health because he's handled it just fine, but we figured it would be good to know in terms of avoiding spreading it to other people.

So we called and set up an appointment. They got us in like an hour and half after we called.

Got there and the doctor said, "Nope, no need for a test."

At this point I'm extremely skeptical that the number counts are in any way accurate. Also I've lost faith in the "we're not doing enough testing" argument since we went and tried to get tested and they turned us away.

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

#42

Post by watwut »

jupp0r wrote: post #34
timr wrote: post #20

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. Rt is simply notation of an estimate of R0 at a particular time. Either way, you're correct that "herd immunity", as used here, means the point at which time the infection rate begins to decline, and this is conditional on population behaviors. If people mix more fre…

> 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.

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

#43

Post by sarchertech »

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…

Conservative people are much more likely to live in rural areas. Liberals in more urban areas. Viruses spread much more effectively in higher population densities.

So you'd really need to look at per capita infection rates and control for density, not absolute numbers.

For some anecdata, in my moderate county we have a mask mandate. The surrounding less populated and much more conservative areas don't. Since the mask mandate was put in place more than half of the cases in my county's hospitals have been from the surrounding counties. Despite that fact that they have an order of magnitude fewer people, and despite that fact that we have far more people living in poverty in absolute terms than they do.

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

#44

Post by whoisburbansky »

jupp0r wrote: post #34
timr wrote: post #20

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. Rt is simply notation of an estimate of R0 at a particular time. Either way, you're correct that "herd immunity", as used here, means the point at which time the infection rate begins to decline, and this is conditional on population behaviors. If people mix more fre…

> 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…

The next paragraph calls out that R0 is not a biological constant specific to a pathogen as it is affected by environment and behavior.

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

#45

Post by nradov »

streptomycin wrote: post #22

https://www.medrxiv.org/content/10.1101/2020.07.23.20160762v... was a similar study a couple months ago that estimated 10-20%, rather than the 34.2-47.5% in this paper. The bigger question is how long immunity lasts, which is still not known.

Immunity isn't a binary condition which lasts for a certain length of time and then stops. It exists on a spectrum. The best evidence we have indicates that most recovered patients will retain a significant level of immunity for at least several years.

https://www.jimmunol.org/content/early/2020/09/03/jimmunol.2...

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

#46

Post by [deleted] »

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?

[deleted]

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

#47

Post by watwut »

war1025 wrote: post #41
seanalltogether wrote: post #7

Earlier quoted context omitted.

I thought I remembered reading early on that icelandic testing was showing that 50% of all people infected there showed no symptoms. Then add on how many people show symptoms but its not severe enough to get tested.

> Then add on how many people show symptoms but its not severe enough to get tested. Earlier this week we took my son in because: 1. Our neighbors have recently recovered from Coronavirus 2. Our son had a cold / fever around the same time lasting several days 3. He had several days of diarrhea after the cold symptoms subsided I talked to my coworker whose wife is a doctor and he relayed the symptoms to her and she sa…

> Also I've lost faith in the "we're not doing enough testing" argument since we went and tried to get tested and they turned us away.

That does not imply that there is enough testing. That just implies that your doctor or health care system is unwilling to test someone in your circumstances. "Not doing enough testing" is not referring to just test kids not being available, it is also referring to health system policies and willingness/unwilingness to test people.

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

#48

Post by jupp0r »

jacquesm wrote: post #33
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…

> R0, which is a constant inherent to the virus strain I think you just devalued your argument. https://wwwnc.cdc.gov/eid/article/25/1/17-1901_article

Thanks for pointing that out, I corrected the post. It wasn't really important to my point though, which is that we might have enough immunity to let the infections die without football games, while we still have growth with football games.

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

#49

Post by jayd16 »

jackpeterfletch wrote: post #30
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…

This is fag packet math, so I'll spare any exact figures. But if the second wave data for the UK is anything to go by, confirmed cases vs actual cases was at _least_ 5x for the first wave. There obivously are other factors, but with increased testing that multiplier only climbs, bringing herd immunity numbers actually within reasonable grasp. I strongly suspect there have been similar effects in the US.

>This is fag packet math

Is this what they call napkin math in the UK? Back of the cigarette pack math?

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

#50

Post by oasisbob »

jacquesm wrote: post #33
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…

> R0, which is a constant inherent to the virus strain I think you just devalued your argument. https://wwwnc.cdc.gov/eid/article/25/1/17-1901_article

I think a big part of the confusion here is how do you clarify the meaning of R0 versus Rt in a context where people don't know the difference, and are using R0 in a context where there is either a time component or obvious public health interventions.

R0 may be a weak theoretical construct, but saying that it's also contextual and not inherent to the virus doesn't do much to clear things up.

http://web.stanford.edu/~jhj1/teachingdocs/Jones-on-R0.pdf

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