10 ms·

This is another really great reason why the herd immunity threshold is lower than it has naively been claimed. If the effect is as large as TFA says then the th

by zaroth 6y ago

This is another really great reason why the herd immunity threshold is lower than it has naively been claimed. If the effect is as large as TFA says then the threshold is actually much lower than the ~60% level. This has a big impact on the estimated death rate for achieving herd immunity. The other factor in that estimate is the CFR which is also plummeting over the summer, although there’s reason to believe CFR could go back up somewhat in the winter depending on how much the gain was environment versus how much is due to better treatment protocols and therapeutics. For example, if the immunity threshold goes from 60% -> 20% and the CFR goes from 5% -> 1% the estimate death toll is reduced to 1/15th (6.6%) of the original estimates.

xorfish 6y ago
Not really, "immune" people can still contract and transmit the virus. So the effect of T-Cell immunity is already accounted for in R0 and IFR estimates.
lukeschlather 6y ago
> This is another really great reason why the herd immunity threshold is lower than it has naively been claimed. It sounds like you're starting from the happy assumption - herd immunity is much easier to achieve than we believe - and working backward to find data which justify your hope. To get good predictions, we have to be dispassionate and not assume the happy case. A realistic assessment would probably assign some sort of a probability range to different thresholds - a model might suggest there's a 60% chance the threshold is 60%, a 5% chance it is 40%, a 20% chance it is 80%, a 10% chance it is 90%. And any model has to take into account that any piece of data might be wrong, including this data about T-cell immunity.
- modeless 6y ago
  In my area, as in Sweden, cases have been declining for many weeks now. Lockdown didn't become stricter. People didn't become more compliant; rather the opposite. Why aren't cases skyrocketing the way they were a couple of months ago? What explanation is there other than the herd immunity thresholds being wrong?
  - null_object 6y ago
    >What explanation is there other than the herd immunity thresholds being wrong? Just to give two possible alternative reasons: - outdoor life over the summer, leading to higher vitamin D levels; - older people are more likely to still be living in their summer cottages. Have you noticed that the death rate is possibly creeping upwards again? It’s simply too early to say. When I arrived back in Stockholm (from the countryside) three weeks ago, the town was very empty: our family was alone eating lunch in a central Italian restaurant on a Sunday. Now the streets are full again, but covid takes 3-4 weeks to take hold again. Not that I expect to see the levels of sickness from April again. But there’s a long winter still ahead of us.
  - meddlepal 6y ago
    Mask compliance is reducing spread?
    - jtbayly 6y ago
      Sweden has recommended against wearing masks. So mask "compliance" would mean not wearing one, which should have led to an explosion of cases, no?
      - alkonaut 6y ago
        I’d say there has just not been a recommendation or mandate to wear them. There hasn’t been a recommendation against them. It could still happen they say, at least regionally e.g in public transport in one region for example.
    - deleted 6y ago
      [deleted]
    - nradov 6y ago
      A recent survey found only 6% mask compliance in Sweden so that's probably not a significant factor. There must be something else going on. https://www.telegraph.co.uk/travel/destinations/europe/sweden/articles/what-life-is-really-like-in-lockdown-hating-sweden/ https://www.telegraph.co.uk/travel/destinations/europe/swede...
- tyingq 6y ago
  The COVID "new cases" data for New York state seem to show something like herd immunity, despite numbers that should be well below herd immunity. I suppose it could be something else, like New York residents being more diligent about masks, social distance, etc. Anecdotally, though, that doesn't seem to be the case.
  - ineedasername 6y ago
    NYC still seems like a ghost town to me.
  - dasudasu 6y ago
    Could be something like people with behaviors consistent with a higher risk of catching/spreading it being already immune by now.
    - username90 6y ago
      That is a factor in herd immunity though.
  - henrikschroder 6y ago
    Almost no one is wearing a mask in Sweden, and the current daily numbers look a lot like NY and NJ.
  - Terretta 6y ago
    Partly NYC is relatively empty and relatively cautious since it was present and real, but partly it’s likely many times more folks have had it in NYC than has been widely reported, possibly one or two orders of magnitude more, leaving fewer candidates now. If, back in the spring, you worked backwards from NYC deaths using mortality rates within the lowest ranges in US studies, then it seemed likely that before summer infections may have already approached most of the population. Mortality rates of 0.5% would have a far higher number of infected, as noted in this April suggestion of much wider prevalence, which if the case ”the real number of infected people in LA County would be 28 to 55 times higher” — https://www.webmd.com/lung/news/20200424/more-data-bolsters-higher-covid-prevalence https://www.webmd.com/lung/news/20200424/more-data-bolsters-... Aside from that math, a variety of sources suggest perhaps 25% of New Yorkers infected in April, such as: A claim in June of ”roughly 25% by June” — https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-york-city-has-probably-been-infected-with-coronavirus-dr-scott-gottlieb-says.html https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-yor... A July claim (opinion piece, not an epidemiologist) of an even earlier peak, Feb and March: ”With a city population estimated by the Census Bureau at 8,336,817, the 22.7% prevalence from the late-April state survey would mean that nearly 1.9 million New Yorkers had already contracted the disease as of early April.” — https://www.bloomberg.com/opinion/articles/2020-07-23/new-york-city-s-covid-19-peak-likely-occurred-in-march-not-april https://www.bloomberg.com/opinion/articles/2020-07-23/new-yo... A July claim that ”over 60% of residents in some boroughs tested positive for the virus.”: https://abcnews.go.com/Health/nyc-neighborhoods-obtained-herd-immunity-study-suggests/story?id=71692365 https://abcnews.go.com/Health/nyc-neighborhoods-obtained-her...
- zaroth 6y ago
  There’s a naive equation for herd immunity which takes the unmitigated transmission rate or R0 of ~3 and calculates 1 - 1/R0 = .66. This is the upper limit on the threshold (what I call the “naive herd immunity rate”) assuming there are no unaccounted for effects which would otherwise reduce R0. Improved personal hygiene, social distancing, PPE, contact tracing, are all various behavioral ways that we have reduced the transmission rate below 2, which reduces the herd immunity needed to get transmission below 1 as long as those measures persist. Another way to say this is that if social measures get us to 1.3 then the infection still spreads until ~25% are infected. The natural immunity discussed in the article is effectively a free boost to your current herd immunity rate. If serological studies show 20% had been infected, but then you can add another 30% on top of that, you are effectively already at 50% herd immunity. I’m not sure what you mean by starting from a happy assumption. The real world data shows us that there is irrefutably something working to either reduce R0 or effectively boost the herd immunity level which isn’t showing up in the serological studies. TFA refers to several studies which show scientific evidence of a biological process that can explain what’s happening in the real world. We can accurately estimate the Rt by just looking at positivity rates, test count, and positive case count. Either R0 is much lower than initially calculated, or effective immunity level is higher than serology tests have shown. I suppose you can pick one, but Sweden at least is a strong datapoint that it’s a function of immunity not social suppression measures.
adventured 6y ago
And then factor in that about 1/2 of all Covid deaths (in the US) are in people over the age of 75 (a population of just 22m). A focus on vaccinating that demographic will quickly, dramatically reduce the mortality rate of Covid. Out of the 104 million people under the age of 25 in the US, only ~400 people have died from Covid. Out of 220 million people under the age of 55, there have only been ~15,000 deaths. We have a very blatant demographic target that we can focus on to rapidly knock down the mortality rate.
- dmurray 6y ago
  The main challenge for vaccines is currently the R+D, not manufacturing enough doses.
  - dahdum 6y ago
    The mRNA vaccines being tested may need down to -70°C cold storage during transport and immediately before use, so quite a logistical challenge. Prioritizing those most at risk will be critical to knocking down the CFR dramatically.
    - guenthert 6y ago
      > to -70°C cold storage during transport and immediately before use, so quite a logistical challenge. Liquid N2. The same is done, e.g. for bull sperma. This isn't an insurmountable challenge.
      - bluGill 6y ago
        Liquid N2 is common in industry. There are national and local companies with branches scattered all over the US that can supply liquid N2 to anyone equipped to handle it. Since doctors use N2 (to freeze warts) they know how to deliver medial grade N2 (if there is such a thing). Those suppliers will work with their normal customers to ensure medical use gets what they need (if arranged in advance they can produce less in exchange for a vaccine for their employees which ultimately means better profits) That is N2 isn't a supply problem. However there are other logistical problems. Most industry uses of N2 are in very large quantities and so the ability to fill a millions of vial sized containers of N2 might not exist even though more than enough N2 exists.
sprite 6y ago
If you look at Atlanta cases are way down and everything is open. People go out to bars, nightclubs, strip clubs, etc. There is not much social distancing and only place I see people wear masks at is the grocery store. I feel like a lot of people that get it and are younger don't get tested and just stay home and ride it out. So the actual cases vs reported cases are a lot higher.
newacct583 6y ago
> the estimate death toll is reduced to 1/15th (6.6%) of the original estimates A million people are dead of this virus already. Which "original estimates" are you citing that predicted 15M people dead? Those line up with the absolute worst case scenarios, not actual predictions.
- zaroth 6y ago
  Well,... for example, the National Institute for Health Research University College London predicted ~580k excess 1-year mortality in a "do nothing" scenario in their "high" relative-risk (RR) assessment. That's ~0.9% of the population in 1 year, or 70 million people if extrapolated worldwide. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30854-0/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
  - zaroth 6y ago
    Oh, and just for fun, this is MSNBC yesterday; “ Math on Trump Covid strategy has millions dying before it works” “2.97% fatality rate * 215,000,000 = 6,385,500 dead” https://www.msnbc.com/rachel-maddow/watch/math-on-trump-covid-strategy-has-millions-dying-before-it-works-91958341539 https://www.msnbc.com/rachel-maddow/watch/math-on-trump-covi...
WhompingWindows 6y ago
"The original estimates" Look at this range of epidemiologists' 2020 death toll estimates (second chart below), gathered by 538 on April 2nd. Comparing to the current death total of 200k in the US, It's actually pretty decent, the majority of experts' ranges include 250k, which may be around where we end up in 2.5 months' time. https://fivethirtyeight.com/features/best-case-and-worst-case-coronavirus-forecasts-are-very-far-apart/ https://fivethirtyeight.com/features/best-case-and-worst-cas... I would take any cruise-ship analysis from early on with a grain of salt. It's very hard to test a pandemic extremely early on, there are less valid and reliable testing instruments.

by zaroth 6y ago

xorfish 6y ago

Not really, "immune" people can still contract and transmit the virus. So the effect of T-Cell immunity is already accounted for in R0 and IFR estimates.

lukeschlather 6y ago

> This is another really great reason why the herd immunity threshold is lower than it has naively been claimed. It sounds like you're starting from the happy assumption - herd immunity is much easier to achieve than we believe - and working backward to find data which justify your hope. To get good predictions, we have to be dispassionate and not assume the happy case. A realistic assessment would probably assign some sort of a probability range to different thresholds - a model might suggest there's a 60% chance the threshold is 60%, a 5% chance it is 40%, a 20% chance it is 80%, a 10% chance it is 90%. And any model has to take into account that any piece of data might be wrong, including this data about T-cell immunity.

modeless 6y ago
In my area, as in Sweden, cases have been declining for many weeks now. Lockdown didn't become stricter. People didn't become more compliant; rather the opposite. Why aren't cases skyrocketing the way they were a couple of months ago? What explanation is there other than the herd immunity thresholds being wrong?
- null_object 6y ago
  >What explanation is there other than the herd immunity thresholds being wrong? Just to give two possible alternative reasons: - outdoor life over the summer, leading to higher vitamin D levels; - older people are more likely to still be living in their summer cottages. Have you noticed that the death rate is possibly creeping upwards again? It’s simply too early to say. When I arrived back in Stockholm (from the countryside) three weeks ago, the town was very empty: our family was alone eating lunch in a central Italian restaurant on a Sunday. Now the streets are full again, but covid takes 3-4 weeks to take hold again. Not that I expect to see the levels of sickness from April again. But there’s a long winter still ahead of us.
- meddlepal 6y ago
  Mask compliance is reducing spread?
  - jtbayly 6y ago
    Sweden has recommended against wearing masks. So mask "compliance" would mean not wearing one, which should have led to an explosion of cases, no?
    - alkonaut 6y ago
      I’d say there has just not been a recommendation or mandate to wear them. There hasn’t been a recommendation against them. It could still happen they say, at least regionally e.g in public transport in one region for example.
  - deleted 6y ago
    [deleted]
  - nradov 6y ago
    A recent survey found only 6% mask compliance in Sweden so that's probably not a significant factor. There must be something else going on. https://www.telegraph.co.uk/travel/destinations/europe/sweden/articles/what-life-is-really-like-in-lockdown-hating-sweden/ https://www.telegraph.co.uk/travel/destinations/europe/swede...
tyingq 6y ago
The COVID "new cases" data for New York state seem to show something like herd immunity, despite numbers that should be well below herd immunity. I suppose it could be something else, like New York residents being more diligent about masks, social distance, etc. Anecdotally, though, that doesn't seem to be the case.
- ineedasername 6y ago
  NYC still seems like a ghost town to me.
- dasudasu 6y ago
  Could be something like people with behaviors consistent with a higher risk of catching/spreading it being already immune by now.
  - username90 6y ago
    That is a factor in herd immunity though.
- henrikschroder 6y ago
  Almost no one is wearing a mask in Sweden, and the current daily numbers look a lot like NY and NJ.
- Terretta 6y ago
  Partly NYC is relatively empty and relatively cautious since it was present and real, but partly it’s likely many times more folks have had it in NYC than has been widely reported, possibly one or two orders of magnitude more, leaving fewer candidates now. If, back in the spring, you worked backwards from NYC deaths using mortality rates within the lowest ranges in US studies, then it seemed likely that before summer infections may have already approached most of the population. Mortality rates of 0.5% would have a far higher number of infected, as noted in this April suggestion of much wider prevalence, which if the case ”the real number of infected people in LA County would be 28 to 55 times higher” — https://www.webmd.com/lung/news/20200424/more-data-bolsters-higher-covid-prevalence https://www.webmd.com/lung/news/20200424/more-data-bolsters-... Aside from that math, a variety of sources suggest perhaps 25% of New Yorkers infected in April, such as: A claim in June of ”roughly 25% by June” — https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-york-city-has-probably-been-infected-with-coronavirus-dr-scott-gottlieb-says.html https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-yor... A July claim (opinion piece, not an epidemiologist) of an even earlier peak, Feb and March: ”With a city population estimated by the Census Bureau at 8,336,817, the 22.7% prevalence from the late-April state survey would mean that nearly 1.9 million New Yorkers had already contracted the disease as of early April.” — https://www.bloomberg.com/opinion/articles/2020-07-23/new-york-city-s-covid-19-peak-likely-occurred-in-march-not-april https://www.bloomberg.com/opinion/articles/2020-07-23/new-yo... A July claim that ”over 60% of residents in some boroughs tested positive for the virus.”: https://abcnews.go.com/Health/nyc-neighborhoods-obtained-herd-immunity-study-suggests/story?id=71692365 https://abcnews.go.com/Health/nyc-neighborhoods-obtained-her...
zaroth 6y ago
There’s a naive equation for herd immunity which takes the unmitigated transmission rate or R0 of ~3 and calculates 1 - 1/R0 = .66. This is the upper limit on the threshold (what I call the “naive herd immunity rate”) assuming there are no unaccounted for effects which would otherwise reduce R0. Improved personal hygiene, social distancing, PPE, contact tracing, are all various behavioral ways that we have reduced the transmission rate below 2, which reduces the herd immunity needed to get transmission below 1 as long as those measures persist. Another way to say this is that if social measures get us to 1.3 then the infection still spreads until ~25% are infected. The natural immunity discussed in the article is effectively a free boost to your current herd immunity rate. If serological studies show 20% had been infected, but then you can add another 30% on top of that, you are effectively already at 50% herd immunity. I’m not sure what you mean by starting from a happy assumption. The real world data shows us that there is irrefutably something working to either reduce R0 or effectively boost the herd immunity level which isn’t showing up in the serological studies. TFA refers to several studies which show scientific evidence of a biological process that can explain what’s happening in the real world. We can accurately estimate the Rt by just looking at positivity rates, test count, and positive case count. Either R0 is much lower than initially calculated, or effective immunity level is higher than serology tests have shown. I suppose you can pick one, but Sweden at least is a strong datapoint that it’s a function of immunity not social suppression measures.

adventured 6y ago

And then factor in that about 1/2 of all Covid deaths (in the US) are in people over the age of 75 (a population of just 22m). A focus on vaccinating that demographic will quickly, dramatically reduce the mortality rate of Covid. Out of the 104 million people under the age of 25 in the US, only ~400 people have died from Covid. Out of 220 million people under the age of 55, there have only been ~15,000 deaths. We have a very blatant demographic target that we can focus on to rapidly knock down the mortality rate.

dmurray 6y ago
The main challenge for vaccines is currently the R+D, not manufacturing enough doses.
- dahdum 6y ago
  The mRNA vaccines being tested may need down to -70°C cold storage during transport and immediately before use, so quite a logistical challenge. Prioritizing those most at risk will be critical to knocking down the CFR dramatically.
  - guenthert 6y ago
    > to -70°C cold storage during transport and immediately before use, so quite a logistical challenge. Liquid N2. The same is done, e.g. for bull sperma. This isn't an insurmountable challenge.
    - bluGill 6y ago
      Liquid N2 is common in industry. There are national and local companies with branches scattered all over the US that can supply liquid N2 to anyone equipped to handle it. Since doctors use N2 (to freeze warts) they know how to deliver medial grade N2 (if there is such a thing). Those suppliers will work with their normal customers to ensure medical use gets what they need (if arranged in advance they can produce less in exchange for a vaccine for their employees which ultimately means better profits) That is N2 isn't a supply problem. However there are other logistical problems. Most industry uses of N2 are in very large quantities and so the ability to fill a millions of vial sized containers of N2 might not exist even though more than enough N2 exists.

sprite 6y ago

If you look at Atlanta cases are way down and everything is open. People go out to bars, nightclubs, strip clubs, etc. There is not much social distancing and only place I see people wear masks at is the grocery store. I feel like a lot of people that get it and are younger don't get tested and just stay home and ride it out. So the actual cases vs reported cases are a lot higher.

newacct583 6y ago

> the estimate death toll is reduced to 1/15th (6.6%) of the original estimates A million people are dead of this virus already. Which "original estimates" are you citing that predicted 15M people dead? Those line up with the absolute worst case scenarios, not actual predictions.

zaroth 6y ago
Well,... for example, the National Institute for Health Research University College London predicted ~580k excess 1-year mortality in a "do nothing" scenario in their "high" relative-risk (RR) assessment. That's ~0.9% of the population in 1 year, or 70 million people if extrapolated worldwide. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30854-0/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
- zaroth 6y ago
  Oh, and just for fun, this is MSNBC yesterday; “ Math on Trump Covid strategy has millions dying before it works” “2.97% fatality rate * 215,000,000 = 6,385,500 dead” https://www.msnbc.com/rachel-maddow/watch/math-on-trump-covid-strategy-has-millions-dying-before-it-works-91958341539 https://www.msnbc.com/rachel-maddow/watch/math-on-trump-covi...

WhompingWindows 6y ago

"The original estimates" Look at this range of epidemiologists' 2020 death toll estimates (second chart below), gathered by 538 on April 2nd. Comparing to the current death total of 200k in the US, It's actually pretty decent, the majority of experts' ranges include 250k, which may be around where we end up in 2.5 months' time. https://fivethirtyeight.com/features/best-case-and-worst-case-coronavirus-forecasts-are-very-far-apart/ https://fivethirtyeight.com/features/best-case-and-worst-cas... I would take any cruise-ship analysis from early on with a grain of salt. It's very hard to test a pandemic extremely early on, there are less valid and reliable testing instruments.