Read on Twitter
1/X
Those behind the Great Barrington Declaration mention herd immunity as a way to address COVID-19.
So I'll discuss it. After all, noting herd immunity (in response to vaccine deniers) is 1 main reason I started on Twitter.
https://twitter.com/AtomsksSanakan/status/891040491214688257
https://gbdeclaration.org/
Those behind the Great Barrington Declaration mention herd immunity as a way to address COVID-19.
So I'll discuss it. After all, noting herd immunity (in response to vaccine deniers) is 1 main reason I started on Twitter.
https://twitter.com/AtomsksSanakan/status/891040491214688257
https://gbdeclaration.org/
2/X
Suppose u want to know how many people would die from COVID-19 under *baseline conditions*.
So basically: treat COVID-19 like another typical disease, with business-as-usual and acting the same as this time last year without the pandemic. https://twitter.com/AtomsksSanakan/status/1337238156052226050
Suppose u want to know how many people would die from COVID-19 under *baseline conditions*.
So basically: treat COVID-19 like another typical disease, with business-as-usual and acting the same as this time last year without the pandemic. https://twitter.com/AtomsksSanakan/status/1337238156052226050
3/X
Re: "how many people would die from COVID-19 under *baseline conditions*"
One can figure that out using:
- the number of people who would get infected
- how many of those infected people die of COVID-19
A separate thread on the latter point: https://twitter.com/AtomsksSanakan/status/1341443629349543937
Re: "how many people would die from COVID-19 under *baseline conditions*"
One can figure that out using:
- the number of people who would get infected
- how many of those infected people die of COVID-19
A separate thread on the latter point: https://twitter.com/AtomsksSanakan/status/1341443629349543937
4/X
The virus infects more people if the virus is more contagious, meaning it has a larger R0.
R0 of 2 implies each infected person infects 2 other people on average, at baseline, before they stop being infectious.
For R0 of 3, they infect 3 others.
Etc
https://www.mdpi.com/2076-393X/8/2/236/htm
The virus infects more people if the virus is more contagious, meaning it has a larger R0.
R0 of 2 implies each infected person infects 2 other people on average, at baseline, before they stop being infectious.
For R0 of 3, they infect 3 others.
Etc
https://www.mdpi.com/2076-393X/8/2/236/htm
5/X
Eventually, so many people become non-infectious + immune to infection, that the virus struggles to find non-immune people to infect and use to infect other non-immune people.
That's the idea behind herd immunity.
https://medium.com/@silentn2040/the-dangerous-myth-that-sweden-achieved-herd-immunity-fd2579526b8b
Eventually, so many people become non-infectious + immune to infection, that the virus struggles to find non-immune people to infect and use to infect other non-immune people.
That's the idea behind herd immunity.
https://medium.com/@silentn2040/the-dangerous-myth-that-sweden-achieved-herd-immunity-fd2579526b8b
6/X
The 'herd immunity threshold' (HIT) is the proportion of people who need to be immune to infection, in order for 'infections per unit time' to stop increasing (i.e. keep R under 1), at baseline.
At HIT, the outbreak is on its way to dying out. https://twitter.com/AtomsksSanakan/status/1309297907863035904
The 'herd immunity threshold' (HIT) is the proportion of people who need to be immune to infection, in order for 'infections per unit time' to stop increasing (i.e. keep R under 1), at baseline.
At HIT, the outbreak is on its way to dying out. https://twitter.com/AtomsksSanakan/status/1309297907863035904
7/X
The classic calculation for HIT is:
1 - (1 / R0)
So an R0 of 3 implies:
HIT = 1 - (1/3) = 67%
A larger R0 means a larger the HIT.
In other words: a more contagious virus means more people need to be immune to infection for the outbreak to die out.
https://www.sciencedirect.com/science/article/pii/S1074761320301709
The classic calculation for HIT is:
1 - (1 / R0)
So an R0 of 3 implies:
HIT = 1 - (1/3) = 67%
A larger R0 means a larger the HIT.
In other words: a more contagious virus means more people need to be immune to infection for the outbreak to die out.
https://www.sciencedirect.com/science/article/pii/S1074761320301709
8/X
Different places have different baseline conditions, + thus different values for R0 and HIT.
https://www.journalofinfection.com/article/S0163-4453(20)30154-7/fulltext
A typical R0 for a western country is ~2.5 or more, implying at HIT of >= 60%. Higher than seasonal flu.
https://link.springer.com/article/10.1186/1471-2334-14-480
https://www.thelancet.com/action/showPdf?pii=S1473-3099%2820%2930484-9
Different places have different baseline conditions, + thus different values for R0 and HIT.
https://www.journalofinfection.com/article/S0163-4453(20)30154-7/fulltext
A typical R0 for a western country is ~2.5 or more, implying at HIT of >= 60%. Higher than seasonal flu.
https://link.springer.com/article/10.1186/1471-2334-14-480
https://www.thelancet.com/action/showPdf?pii=S1473-3099%2820%2930484-9
9/x
People still get infected after HIT is reached, but not enough to replace the people who become immune after they recover from infection (since R is now less than 1).
This implies "overshoot": the final percentage of people infected is more than HIT
https://twitter.com/CT_Bergstrom/status/1252009362849009664
People still get infected after HIT is reached, but not enough to replace the people who become immune after they recover from infection (since R is now less than 1).
This implies "overshoot": the final percentage of people infected is more than HIT
https://twitter.com/CT_Bergstrom/status/1252009362849009664
10/X
So for the question from part 2/X:
How many people would die from COVID-19 under *baseline conditions*?
Ferguson et al. answered this in March, with a HIT of ~58%, and IFR of 0.9% for Great Britain (~0.8% for the USA):
https://twitter.com/AtomsksSanakan/status/1337273174967394305
http://web.archive.org/web/20200421012308/https://spiral.imperial.ac.uk:8443/bitstream/10044/1/77482/14/2020-03-16-COVID19-Report-9.pdf
So for the question from part 2/X:
How many people would die from COVID-19 under *baseline conditions*?
Ferguson et al. answered this in March, with a HIT of ~58%, and IFR of 0.9% for Great Britain (~0.8% for the USA):
https://twitter.com/AtomsksSanakan/status/1337273174967394305
http://web.archive.org/web/20200421012308/https://spiral.imperial.ac.uk:8443/bitstream/10044/1/77482/14/2020-03-16-COVID19-Report-9.pdf
11/X
So how does this play out in reality?
Well, a respiratory virus like SARS-CoV-2 that spreads by droplets + aerosols, takes longer to infect a given proportion of people in:
- a larger population
- a population spread over a wider geographical area https://twitter.com/AtomsksSanakan/status/1292997236843057156
So how does this play out in reality?
Well, a respiratory virus like SARS-CoV-2 that spreads by droplets + aerosols, takes longer to infect a given proportion of people in:
- a larger population
- a population spread over a wider geographical area https://twitter.com/AtomsksSanakan/status/1292997236843057156
12/X
Since SARS-CoV-2 is very contagious (high R0 and therefore high HIT), SARS-CoV-2 then quickly infects a large proportion of people in smaller populations and/or populations covering small areas, before behavior changes and interventions limit spread
https://twitter.com/AtomsksSanakan/status/1293007098134044672
Since SARS-CoV-2 is very contagious (high R0 and therefore high HIT), SARS-CoV-2 then quickly infects a large proportion of people in smaller populations and/or populations covering small areas, before behavior changes and interventions limit spread
https://twitter.com/AtomsksSanakan/status/1293007098134044672
13/X
SARS-CoV-2 also infects a higher proportion of people in areas that remain closer to the baseline conditions of R0 (i.e. not much infection-limiting behavior changes and/or public health interventions like mask-wearing).
https://twitter.com/AtomsksSanakan/status/1323672387121020930
https://web.archive.org/web/20201102030724/https://www.researchgate.net/publication/343414173_Seroprevalence_of_anti-SARS-CoV-2_antibodies_in_the_city_of_Iquitos_Loreto_Peru
SARS-CoV-2 also infects a higher proportion of people in areas that remain closer to the baseline conditions of R0 (i.e. not much infection-limiting behavior changes and/or public health interventions like mask-wearing).
https://twitter.com/AtomsksSanakan/status/1323672387121020930
https://web.archive.org/web/20201102030724/https://www.researchgate.net/publication/343414173_Seroprevalence_of_anti-SARS-CoV-2_antibodies_in_the_city_of_Iquitos_Loreto_Peru
14/X
Larger populations see people dying of COVID-19, and respond with additional behavior changes + public health interventions that push them further from the baseline conditions of R0.
That limits the spread of SARS-CoV-2 and limits COVID-19 deaths.
https://twitter.com/AtomsksSanakan/status/1338578097013219339
Larger populations see people dying of COVID-19, and respond with additional behavior changes + public health interventions that push them further from the baseline conditions of R0.
That limits the spread of SARS-CoV-2 and limits COVID-19 deaths.
https://twitter.com/AtomsksSanakan/status/1338578097013219339
15/X
So larger populations and/or populations spread over larger geographic areas, end up with a lower proportion of people infected, even though HIT is high.
Some people see those lower proportion of infected people, and incorrectly infer HIT is low
https://twitter.com/AtomsksSanakan/status/1283817701316714499
So larger populations and/or populations spread over larger geographic areas, end up with a lower proportion of people infected, even though HIT is high.
Some people see those lower proportion of infected people, and incorrectly infer HIT is low
https://twitter.com/AtomsksSanakan/status/1283817701316714499
16/X
But remember, it wasn't herd immunity that limited infections into larger populations and regions; those regions didn't reach HIT.
Instead, it was behavior changes and/or public health interventions that limited infections
https://twitter.com/AtomsksSanakan/status/1337362849820266500
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289569/
But remember, it wasn't herd immunity that limited infections into larger populations and regions; those regions didn't reach HIT.
Instead, it was behavior changes and/or public health interventions that limited infections
https://twitter.com/AtomsksSanakan/status/1337362849820266500
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289569/
17/X
I'll make a claim some people may find controversial:
Claiming HIT is very low (ex: ~10% - ~20%) is *dangerous and obviously incorrect.*
In fact, it may be the most dangerous idea to emerge during the COVID-19 pandemic.
https://twitter.com/AtomsksSanakan/status/1337240769732767744
https://twitter.com/AtomsksSanakan/status/1337255624854425600
I'll make a claim some people may find controversial:
Claiming HIT is very low (ex: ~10% - ~20%) is *dangerous and obviously incorrect.*
In fact, it may be the most dangerous idea to emerge during the COVID-19 pandemic.
https://twitter.com/AtomsksSanakan/status/1337240769732767744
https://twitter.com/AtomsksSanakan/status/1337255624854425600
18/X
Saying we reached a low HIT tells us we no longer need to go beyond *baseline conditions* to prevent infections/day from increasing; i.e. no additional:
- mask-wearing
- avoiding visiting nursing homes + large indoor gathers
- vaccinations
etc.
https://twitter.com/AtomsksSanakan/status/1292337005918068736
Saying we reached a low HIT tells us we no longer need to go beyond *baseline conditions* to prevent infections/day from increasing; i.e. no additional:
- mask-wearing
- avoiding visiting nursing homes + large indoor gathers
- vaccinations
etc.
https://twitter.com/AtomsksSanakan/status/1292337005918068736
19/X
Some non-experts and experts claim HIT is low.
Examples of non-experts:
https://www.medrxiv.org/content/medrxiv/early/2020/05/22/2020.05.19.20104596.full.pdf
https://www.zerohedge.com/political/whitney-looks-sweden-was-right-after-all
https://realclimatescience.com/2020/06/no-immunity-versus-herd-immunity/
https://off-guardian.org/2020/07/07/second-wave-not-even-close/
https://medium.com/@jrfinkel/covid-putting-the-puzzle-together-3e3a5f333d84
https://twitter.com/RandPaul/status/1283753633247563777
https://judithcurry.com/2020/05/10/why-herd-immunity-to-covid-19-is-reached-much-earlier-than-thought/
https://judithcurry.com/2020/06/28/the-progress-of-the-covid-19-epidemic-in-sweden-an-analysis/
Some non-experts and experts claim HIT is low.
Examples of non-experts:
https://www.medrxiv.org/content/medrxiv/early/2020/05/22/2020.05.19.20104596.full.pdf
https://www.zerohedge.com/political/whitney-looks-sweden-was-right-after-all
https://realclimatescience.com/2020/06/no-immunity-versus-herd-immunity/
https://off-guardian.org/2020/07/07/second-wave-not-even-close/
https://medium.com/@jrfinkel/covid-putting-the-puzzle-together-3e3a5f333d84
https://twitter.com/RandPaul/status/1283753633247563777
https://judithcurry.com/2020/05/10/why-herd-immunity-to-covid-19-is-reached-much-earlier-than-thought/
https://judithcurry.com/2020/06/28/the-progress-of-the-covid-19-epidemic-in-sweden-an-analysis/
20/X
The non-experts have no background in epidemiology, immunology, etc.
So they falsely assume only herd immunity can limit R and thus limit infections per day; i.e. they assume if infections/day and COVID-19 deaths/day decrease, then HIT was reached
https://archive.is/h96zK#selection-23077.0-23105.283
The non-experts have no background in epidemiology, immunology, etc.
So they falsely assume only herd immunity can limit R and thus limit infections per day; i.e. they assume if infections/day and COVID-19 deaths/day decrease, then HIT was reached
https://archive.is/h96zK#selection-23077.0-23105.283
21/X
But factors other than herd immunity can limit infections and deaths, as covered in part 16/X. So the non-experts are wrong.
You can usually spot these non-experts because they claim Stockholm, Sweden (or New York City, or...) reached HIT.
Yet...
https://archive.is/CKncm#selection-17975.0-18009.608
But factors other than herd immunity can limit infections and deaths, as covered in part 16/X. So the non-experts are wrong.
You can usually spot these non-experts because they claim Stockholm, Sweden (or New York City, or...) reached HIT.
Yet...
https://archive.is/CKncm#selection-17975.0-18009.608
22/X
So what about experts who claim HIT is low? Probably the most well-known one is Gabriela M. Gomes ( @mgmgomes1).
Unlike the non-experts, her team is aware that HIT is about baseline conditions of R0.
https://twitter.com/AtomsksSanakan/status/1337240276356751361
https://www.medrxiv.org/content/10.1101/2020.09.26.20202267v1
https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v3.full.pdf
So what about experts who claim HIT is low? Probably the most well-known one is Gabriela M. Gomes ( @mgmgomes1).
Unlike the non-experts, her team is aware that HIT is about baseline conditions of R0.
https://twitter.com/AtomsksSanakan/status/1337240276356751361
https://www.medrxiv.org/content/10.1101/2020.09.26.20202267v1
https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v3.full.pdf
23/X
But the expert proponents of low HIT still need to distinguish the effects of HIT, vs. the effects of behavior changes + public health interventions.
Turns out Gomes' team did that incorrectly.
https://twitter.com/FoxandtheFlu/status/1334546142852337664
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
But the expert proponents of low HIT still need to distinguish the effects of HIT, vs. the effects of behavior changes + public health interventions.
Turns out Gomes' team did that incorrectly.
https://twitter.com/FoxandtheFlu/status/1334546142852337664
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
24/X
When one better accounts for the effects of behavior changes + public health interventions, HIT is >50% (green), instead of ~10% - ~20% (blue).
Achieving this higher HIT, without a vaccine, would cause more COVID-19 deaths.
https://twitter.com/AtomsksSanakan/status/1337217585377660928
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
When one better accounts for the effects of behavior changes + public health interventions, HIT is >50% (green), instead of ~10% - ~20% (blue).
Achieving this higher HIT, without a vaccine, would cause more COVID-19 deaths.
https://twitter.com/AtomsksSanakan/status/1337217585377660928
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
25/X
Other sources also support a HIT of >50%, or HIT still not being reached at a >40% infection rate.
https://web.archive.org/web/20200823103654/https://www.medrxiv.org/content/10.1101/2020.08.20.20178533v1.full.pdf
http://web.archive.org/web/20200901132708/https://www.medrxiv.org/content/10.1101/2020.08.28.20180463v1.full.pdf
"A method is presented for estimating the model parameters from real-world data [...]"
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242132
![25/XOther sources also support a HIT of >50%, or HIT still not being reached at a >40% infection rate. https://web.archive.org/web/20200823103654/https://www.medrxiv.org/content/10.1101/2020.08.20.20178533v1.full.pdf http://web.archive.org/web/20200901132708/https://www.medrxiv.org/content/10.1101/2020.08.28.20180463v1.full.pdf"A method is presented for estimating the model parameters from real-world data [...]" https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242132](https://pbs.twimg.com/media/Ep819O5W4AEistg.png "25/XOther sources also support a HIT of >50%, or HIT still not being reached at a >40% infection rate. https://web.archive.org/web/20200823103654/https://www.medrxiv.org/content/10.1101/2020.08.20.20178533v1.full.pdf http://web.archive.org/web/20200901132708/https://www.medrxiv.org/content/10.1101/2020.08.28.20180463v1.full.pdf\"A method is presented for estimating the model parameters from real-world data [...]\" https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242132")
Other sources also support a HIT of >50%, or HIT still not being reached at a >40% infection rate.
https://web.archive.org/web/20200823103654/https://www.medrxiv.org/content/10.1101/2020.08.20.20178533v1.full.pdf
http://web.archive.org/web/20200901132708/https://www.medrxiv.org/content/10.1101/2020.08.28.20180463v1.full.pdf
"A method is presented for estimating the model parameters from real-world data [...]"
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242132
26/X
Why think HIT is high?
One reason centers on heterogeneity vs. homogeneity.
Or in layman's terms: differences vs. sameness.
The "HIT = 1 - (1 / R0)" calculation from part 7/X assumes sameness, while low HIT proponents claim large differences.
https://www.sciencedirect.com/science/article/pii/S1074761320301709
Why think HIT is high?
One reason centers on heterogeneity vs. homogeneity.
Or in layman's terms: differences vs. sameness.
The "HIT = 1 - (1 / R0)" calculation from part 7/X assumes sameness, while low HIT proponents claim large differences.
https://www.sciencedirect.com/science/article/pii/S1074761320301709
27/X
If "heterogeneity vs. homogeneity" is confusing, think of a sexually-transmitted infection (STI) like HIV.
With STIs, heterogeneity is high (so large differences virus transmission interactions).
https://twitter.com/bansallab/status/1259970552074207238
https://cambridge.org/core/services/aop-cambridge-core/content/view/C24D3E55E075B29059AF654BB6D84576/S1446181113000035a.pdf/spatial_heterogeneity_in_simple_deterministic_sir_models_assessed_ecologically.pdf
https://archive.is/qBEuG#selection-19093.0-19093.887
If "heterogeneity vs. homogeneity" is confusing, think of a sexually-transmitted infection (STI) like HIV.
With STIs, heterogeneity is high (so large differences virus transmission interactions).
https://twitter.com/bansallab/status/1259970552074207238
https://cambridge.org/core/services/aop-cambridge-core/content/view/C24D3E55E075B29059AF654BB6D84576/S1446181113000035a.pdf/spatial_heterogeneity_in_simple_deterministic_sir_models_assessed_ecologically.pdf
https://archive.is/qBEuG#selection-19093.0-19093.887
28/X
But SARS-CoV-2, the virus that causes the disease COVID-19, isn't an STI. It's a respiratory virus spread by droplets + aerosols, using behaviors more common to everyone, such as breathing + face-touching
So there's more sameness (i.e. homogeneity)
https://www.quantamagazine.org/the-tricky-math-of-covid-19-herd-immunity-20200630/
But SARS-CoV-2, the virus that causes the disease COVID-19, isn't an STI. It's a respiratory virus spread by droplets + aerosols, using behaviors more common to everyone, such as breathing + face-touching
So there's more sameness (i.e. homogeneity)
https://www.quantamagazine.org/the-tricky-math-of-covid-19-herd-immunity-20200630/
29/X
Ironically, many non-experts try to lecture me on how heterogeneity (differences) are large for SARS-CoV-2, when they know less about this than me.
Highlights in tweets in part 30/X onwards, in case they try this on you.
https://twitter.com/VicenteAriztia/status/1289397995092484096
https://twitter.com/AtomsksSanakan/status/891040491214688257
Ironically, many non-experts try to lecture me on how heterogeneity (differences) are large for SARS-CoV-2, when they know less about this than me.
Highlights in tweets in part 30/X onwards, in case they try this on you.
https://twitter.com/VicenteAriztia/status/1289397995092484096
https://twitter.com/AtomsksSanakan/status/891040491214688257
30/X
Different T cell responses between people won't give enough heterogeneity to greatly lower HIT, especially since T cells are not primarily involved in limiting infections. They're more about responding after infection.
https://twitter.com/profshanecrotty/status/1309170532965920769
https://twitter.com/AtomsksSanakan/status/1309311345947484166
Different T cell responses between people won't give enough heterogeneity to greatly lower HIT, especially since T cells are not primarily involved in limiting infections. They're more about responding after infection.
https://twitter.com/profshanecrotty/status/1309170532965920769
https://twitter.com/AtomsksSanakan/status/1309311345947484166
31/X
In layman's terms: cross-reactivity involves the immune system treating SARS-CoV-2 like another virus the immune system previously responded to, such as another coronavirus.
Cross-reactivity isn't going to drop HIT by a lot
https://twitter.com/AtomsksSanakan/status/1312654302742183936
https://www.nature.com/articles/s41577-020-00460-4
In layman's terms: cross-reactivity involves the immune system treating SARS-CoV-2 like another virus the immune system previously responded to, such as another coronavirus.
Cross-reactivity isn't going to drop HIT by a lot
https://twitter.com/AtomsksSanakan/status/1312654302742183936
https://www.nature.com/articles/s41577-020-00460-4
32/X
There are transmission differences, such as medical professionals generating aerosols when they intubate people (i.e. place tube down their throat), placing those professionals at more risk from SARS-CoV-2-containing aerosols.
http://web.archive.org/web/20201223222714/https://apps.who.int/iris/bitstream/handle/10665/331601/WHO-2019-nCoV-Sci_Brief-Transmission_modes-2020.1-eng.pdf?sequence=1&isAllowed=y
There are transmission differences, such as medical professionals generating aerosols when they intubate people (i.e. place tube down their throat), placing those professionals at more risk from SARS-CoV-2-containing aerosols.
http://web.archive.org/web/20201223222714/https://apps.who.int/iris/bitstream/handle/10665/331601/WHO-2019-nCoV-Sci_Brief-Transmission_modes-2020.1-eng.pdf?sequence=1&isAllowed=y
33/X
But these differences occur for other respiratory viruses such as influenza, w/o causing a much lower-than-expected HIT.
Other pertinent differences are likely already included in R0 (see parts 28/X and 31/X).
https://twitter.com/AdamJKucharski/status/1294985964801142784
https://archive.is/8MiEc#selection-19555.0-19559.843
But these differences occur for other respiratory viruses such as influenza, w/o causing a much lower-than-expected HIT.
Other pertinent differences are likely already included in R0 (see parts 28/X and 31/X).
https://twitter.com/AdamJKucharski/status/1294985964801142784
https://archive.is/8MiEc#selection-19555.0-19559.843
34/X
There isn't perfect sameness (perfect homogeneity).
But it's homogenous enough for a high HIT + to have "HIT = 1 - (1 / R0)" from part 7/X be a decent approximation, consistent with the high infection rates from 12/X + 13/X
https://twitter.com/AtomsksSanakan/status/1339263966678224897
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
There isn't perfect sameness (perfect homogeneity).
But it's homogenous enough for a high HIT + to have "HIT = 1 - (1 / R0)" from part 7/X be a decent approximation, consistent with the high infection rates from 12/X + 13/X
https://twitter.com/AtomsksSanakan/status/1339263966678224897
https://www.medrxiv.org/content/10.1101/2020.12.01.20242289v1.full.pdf
35/X
Proponents of low HIT also predicted areas with high infection rates wouldn't have strong second waves.
They were wrong (another example in part 21/X).
https://twitter.com/OYCar/status/1318386897660518401
https://twitter.com/akcayerol/status/1318376173177606151
https://twitter.com/mikejohansenmd/status/1320453089875447810
https://archive.is/m8e89#selection-22359.0-22889.33
https://twitter.com/thomdvorak/status/1319657564003500032
Proponents of low HIT also predicted areas with high infection rates wouldn't have strong second waves.
They were wrong (another example in part 21/X).
https://twitter.com/OYCar/status/1318386897660518401
https://twitter.com/akcayerol/status/1318376173177606151
https://twitter.com/mikejohansenmd/status/1320453089875447810
https://archive.is/m8e89#selection-22359.0-22889.33
https://twitter.com/thomdvorak/status/1319657564003500032
36/X
Gomes' low HIT framework predicted places with higher infection fatality rates would have lower infection rates.
That didn't consistently hold up.
https://twitter.com/mgmgomes1/status/1310944207901687810
https://www.mdpi.com/2079-7737/9/6/128/htm
https://web.archive.org/web/20200830215825/https://www.preprints.org/manuscript/202008.0648/v1
https://twitter.com/AtomsksSanakan/status/1333154830962094088
https://twitter.com/GidMK/status/1277804390603059201
Gomes' low HIT framework predicted places with higher infection fatality rates would have lower infection rates.
That didn't consistently hold up.
https://twitter.com/mgmgomes1/status/1310944207901687810
https://www.mdpi.com/2079-7737/9/6/128/htm
https://web.archive.org/web/20200830215825/https://www.preprints.org/manuscript/202008.0648/v1
https://twitter.com/AtomsksSanakan/status/1333154830962094088
https://twitter.com/GidMK/status/1277804390603059201
37/X
The observed pattern of infections and COVID-19 deaths better fit one would expect from behavior changes + public health interventions limiting infections, not herd immunity (with a low HIT) limiting infections, as per part 16/X.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289569/
The observed pattern of infections and COVID-19 deaths better fit one would expect from behavior changes + public health interventions limiting infections, not herd immunity (with a low HIT) limiting infections, as per part 16/X.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289569/
38/X
There are other region-specific reasons to think particular regions did not reach a low HIT. I've covered some elsewhere:
https://twitter.com/AtomsksSanakan/status/1282213024905015298
https://medium.com/@silentn2040/the-dangerous-myth-that-sweden-achieved-herd-immunity-fd2579526b8b
There are other region-specific reasons to think particular regions did not reach a low HIT. I've covered some elsewhere:
https://twitter.com/AtomsksSanakan/status/1282213024905015298
https://medium.com/@silentn2040/the-dangerous-myth-that-sweden-achieved-herd-immunity-fd2579526b8b
39/X
So some reasons for thinking the herd immunity threshold is high:
- the biology underlying transmission of respiratory viruses
- high infection rates
- second waves
- higher fatality rates at higher infection rates
etc.
And I've see no good reason to think HIT is very low
So some reasons for thinking the herd immunity threshold is high:
- the biology underlying transmission of respiratory viruses
- high infection rates
- second waves
- higher fatality rates at higher infection rates
etc.
And I've see no good reason to think HIT is very low
40/X
Some folks claim HIT is low, b/c it allows them to downplay how dangerous COVID-19 is + thus avoid policies they dislike (like lockdowns).
Hence why many of the same people who suggest HIT is low, also under-estimated SARS-CoV-2's fatality rate.
https://twitter.com/AtomsksSanakan/status/1314397925016064000
Some folks claim HIT is low, b/c it allows them to downplay how dangerous COVID-19 is + thus avoid policies they dislike (like lockdowns).
Hence why many of the same people who suggest HIT is low, also under-estimated SARS-CoV-2's fatality rate.
https://twitter.com/AtomsksSanakan/status/1314397925016064000
41/X
Also, other factors can increase HIT.
For example: people not becoming immune to infection after they're infected. The "HIT = 1 - (1 / R0)" calculation assumes persistent immunity after infection, as per part 26/X.
https://twitter.com/AtomsksSanakan/status/1316757724387041285
https://archive.is/Xjyec#selection-15423.0-15455.142
Also, other factors can increase HIT.
For example: people not becoming immune to infection after they're infected. The "HIT = 1 - (1 / R0)" calculation assumes persistent immunity after infection, as per part 26/X.
https://twitter.com/AtomsksSanakan/status/1316757724387041285
https://archive.is/Xjyec#selection-15423.0-15455.142
