I don't understand 'Herd Immunity'

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aggievaulter07
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1:45p, 8/13/20
AG
I mean, I get the IDEA of 'Herd Immunity', but why do we expect that to be a thing? We don't have herd immunity from the common cold. We don't have herd immunity from the flu.

So, why do we expect to have herd immunity from COVID at ANY point?

Someone way smarter than me please ELI5 (Explain it like I'm 5)
"I think aggievaulter07 may be the first person on TexAgs to actually back his **** up. I'm astounded, a little confused, and possibly hungry. I need some time to think about what this means." -MW03
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One Eyed Reveille
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1:49p, 8/13/20
AG
Herd immunity doesnt mean you dont get it ever. It means the transmission and viral load is lower. And that the average person has probably already had it and will thus have built up some resistance to it. But not an immunity where they would never get it.
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aggievaulter07
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1:53p, 8/13/20
AG
If the goal is simply 'lower', then using the word "immunity" seems disingenuous.

Overcoming COVID does not make one immune to future infection to COVID any more than getting a cold or the flu does.

I appreciate the response. Maybe I'm still just not getting it.

EDIT: Just saw your edit, but I still don't get it. Having had the flu or a cold doesn't seem to make one more resistant to, or less likely to get the flu or the cold in the future either, but maybe I'm 100% wrong on that.

Maybe I am just looking for real-world examples of herd immunity in action with other infections.
"I think aggievaulter07 may be the first person on TexAgs to actually back his **** up. I'm astounded, a little confused, and possibly hungry. I need some time to think about what this means." -MW03
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beerad12man
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1:59p, 8/13/20
AG
I'm not an expert, but there are a few things to think about here. One, we absolutely do have herd immunity from many common colds and many strands of the flu. Many have died out over the years, but there are hundred of strands of it.

No one is saying it goes away. But that the rate of transmission reduces with enough of the population having it that it basically becomes nothing. Or at least, nothing we should alter life for moving forward. It might still exist on a small scale, and it's possible someone might have a weak response to it and get it again. Though so far, that hasn't been the case with multiple studies.

So a lot of it has to do with the sheer volume as to how many colds and flus there are out there. We have herd immunity to some colds and flus. We have low rate of spread with many of them and many have different defenses against a lot of flus/colds. It's why someone can have a cold, be in a room with others, and many of them not get sick. It might only transfer to a few people over the flu/cold season, and maybe even eventually die out that cycle having effected very few.

One good thing we have going with covid is that coronaviruses don't tend to mutate as quickly as the flu. In general, covid even with it's minor mutations(some say 9 strands) attacks the same way. So if you've beaten it once, in theory you should have a much, much better chance to beat it, or straight up fight if off, again.
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HotardAg07
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1:59p, 8/13/20
AG
ELI5 answer: As more people become immune to a virus, the less likely an infected person is to infect others. At some point the number of people immune is so large that new infections begin to shrink.

The cold and the flu are catch alls for a family of viruses that are constantly mutating and changing, therefore making a moving target. This is why we have flu vaccines every year and why the flu vaccine has limited efficacy every year. They are trying to estimate what the prominent strands of the flu virus will be circulating and create the vaccine for that.
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beerad12man
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In reply to aggievaulter07 • 2:00p, 8/13/20
AG
aggievaulter07 said:
If the goal is simply 'lower', then using the word "immunity" is disingenuous.

Overcoming COVID does not make one immune to future infection to COVID any more than getting a cold or the flu does.

I appreciate the response. Maybe I'm still just not getting it.

EDIT: Just saw your edit, but I still don't get it. Having had the flu or a cold doesn't seem to make one more resistant to, or less likely to get the flu or the cold in the future either, but maybe I'm 100% wrong on that.

Maybe I am just looking for real-world examples of herd immunity in action with other infections.
You are greatly underestimating how many strands there are. Common colds are made up of coronaviruses (I believe about 20%) among others,

You can absolutely be immune to one, but not the other. You can have one last 5 years of immunity, then fade. Or forever. No way to know for sure.

But with ANY SINGLE STRAND of the flu or cold, your odds of getting it twice are much lower than getting it once. At least, from a severe case spectrum.
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aggievaulter07
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In reply to HotardAg07 • 2:01p, 8/13/20
AG
Thanks for the response. So, maybe the answer I am looking for is: "We don't expect COVID-19 to be quite the moving target that the 'Flu' and 'Cold' are because we expect it be more consistent and not mutate on the level that these others do".

Am I on the right path now?
"I think aggievaulter07 may be the first person on TexAgs to actually back his **** up. I'm astounded, a little confused, and possibly hungry. I need some time to think about what this means." -MW03
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SouthTex99
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2:02p, 8/13/20
AG
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beerad12man
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In reply to aggievaulter07 • 2:05p, 8/13/20
AG
Covid is a type of cold. It's just a brand new one that they haven't seen before. It's also part of the reason many seem to be somewhat immune to it. Not that they can't get it, but why 30-40% are either asymptomatic, or have minor symptoms. Potentially because they have some kind of immunity from past coronaviruses.

There are a lot better experts out there than me, and I'm sure a few things I've said aren't necessary facts. But I think it's the general idea.
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HotardAg07
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In reply to aggievaulter07 • 2:05p, 8/13/20
AG
aggievaulter07 said:
Thanks for the response. So, maybe the answer I am looking for is: "We don't expect COVID-19 to be quite the moving target that the 'Flu' and 'Cold' are.

Am I on the right path now?
Studies have shown that COVID-19 is mutating much slower than the seasonal flu, so making it more likely that a vaccine will be effective.
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plain_o_llama
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In reply to aggievaulter07 • 2:06p, 8/13/20
I doubt I'm smarter than you.....

The term is useful in discussing topics in regard to immunity particularly related to vaccination. Even there it is used broadly.


"Herd Immunity": A Rough Guide
https://academic.oup.com/cid/article/52/7/911/299077

The term ''herd immunity'' is widely used but carries a variety of meanings [17]. Some authors use it to describe the proportion immune among individuals in a population. Others use it with reference to a particular threshold proportion of immune individuals that should lead to a decline in incidence of infection. Still others use it to refer to a pattern of immunity that should protect a population from invasion of a new infection. A common implication of the term is that the risk of infection among susceptible individuals in a population is reduced by the presence and proximity of immune individuals (this is sometimes referred to as ''indirect protection'' or a ''herd effect'').

In relation to Covid it is often used to mean something like "a point where we no longer have to engage in mitigation measures" or "a point where we treat it like we treat the common cold or the flu." Some people believe that is now or at least want that to be now. Accordingly, they marshal data, rhetoric, and speculation to support the idea we are there, almost there, or will get there if we do X.

YMMV

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aggievaulter07
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2:11p, 8/13/20
AG
Lots of good responses in here.

Thanks guys!

Definitely makes more sense to me now than before I started this thread.
"I think aggievaulter07 may be the first person on TexAgs to actually back his **** up. I'm astounded, a little confused, and possibly hungry. I need some time to think about what this means." -MW03
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beerad12man
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In reply to aggievaulter07 • 2:16p, 8/13/20
AG
I think the main thing is to remember that the cold isn't one thing. The flu isn't one thing. There are hundreds of colds/flus. As an individual, you can be immune to many, while still get another. There can be 15 flus or colds passing around you every day one winter, and you may only be highly susceptible to getting 1 or 2 of them. As a society, we can be immune to many of these as well, but still pass around another at a higher level.

Covid 19 is one thing. The more people that have it, the less it's spread around. And with Busters posts on the other thread, there seems to be some encouraging stuff of this immunity lasting. Lets hope that continues and Covid 19 stays the same that our bodies keep recognizing it, and that a vaccine is more easily obtained.
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94chem
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5:23p, 8/13/20
Herd immunity is like pushing the control rods into a nuclear reactor, thereby slowing down the rate of productive collisions. A slow burn is still possible, but the herd doesn't have widespread infection. It is a public health term for flattening the curve permanently, but it doesn't reduce your risk of getting ill. It just means you won't get it at the same time as everyone else. Anti-vaxxers rely on others to maintain herd immunity for them, since vaccines basically do the same job as antibodies. In theory, an effective enough vaccine could eradicate a disease, and vaccination wouldn't be necessary. However, anti-vaxxers present a huge risk, even among the vaccinated, but we just don't know whether childhood vaccines confer lifetime immunity.
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MasterAggie
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6:01p, 8/13/20
AG
Quote:
Overcoming COVID does not make one immune to future infection to COVID any more than getting a cold or the flu does.
You don't know any of that and no one knows for sure the ability to develop immunity to COVID 19.
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eric76
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In reply to beerad12man • 6:37p, 8/13/20
AG
beerad12man said:
Covid is a type of cold. It's just a brand new one that they haven't seen before. It's also part of the reason many seem to be somewhat immune to it. Not that they can't get it, but why 30-40% are either asymptomatic, or have minor symptoms. Potentially because they have some kind of immunity from past coronaviruses.

There are a lot better experts out there than me, and I'm sure a few things I've said aren't necessary facts. But I think it's the general idea.
A type of a cold? Really?

Is rabies a type of cold, too? How about polio?

Hint: A cold is a disease of the upper respiratory tract caused by a virus. Covid goes way beyond being a cold.
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Ragoo
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In reply to eric76 • 6:48p, 8/13/20
AG
eric76 said:
beerad12man said:
Covid is a type of cold. It's just a brand new one that they haven't seen before. It's also part of the reason many seem to be somewhat immune to it. Not that they can't get it, but why 30-40% are either asymptomatic, or have minor symptoms. Potentially because they have some kind of immunity from past coronaviruses.

There are a lot better experts out there than me, and I'm sure a few things I've said aren't necessary facts. But I think it's the general idea.
A type of a cold? Really?

Is rabies a type of cold, too? How about polio?

Hint: A cold is a disease of the upper respiratory tract caused by a virus. Covid goes way beyond being a cold.
https://www.cdc.gov/coronavirus/general-information.html
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amercer
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6:56p, 8/13/20
AG
If I had to guess, as a country we are probably in 2-5% immunity range. The hardest hit areas in the world struggle to get above 10-20%, and most of the US has been relatively untouched.

The asymptomatic cases probably account for a lot of that. I doubt those people generate much of an immune response. I do think that if you've had a moderate to severe case you probably can't get it again.

The cross reactivate T cells in a slice of the population are interesting, but we don't know yet how much, if any immunity they provide.
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beerad12man
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In reply to 94chem • 6:56p, 8/13/20
AG
94chem said:
Herd immunity is like pushing the control rods into a nuclear reactor, thereby slowing down the rate of productive collisions. A slow burn is still possible, but the herd doesn't have widespread infection. It is a public health term for flattening the curve permanently, but it doesn't reduce your risk of getting ill. It just means you won't get it at the same time as everyone else. Anti-vaxxers rely on others to maintain herd immunity for them, since vaccines basically do the same job as antibodies. In theory, an effective enough vaccine could eradicate a disease, and vaccination wouldn't be necessary. However, anti-vaxxers present a huge risk, even among the vaccinated, but we just don't know whether childhood vaccines confer lifetime immunity.


Likely a load of drivel for this particular virus.
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beerad12man
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In reply to amercer • 6:58p, 8/13/20
AG
amercer said:
If I had to guess, as a country we are probably in 2-5% immunity range. The hardest hit areas in the world struggle to get above 10-20%, and most of the US has been relatively untouched.

The asymptomatic cases probably account for a lot of that. I doubt those people generate much of an immune response. I do think that if you've had a moderate to severe case you probably can't get it again.

The cross reactivate T cells in a slice of the population are interesting, but we don't know yet how much, if any immunity they provide.


Much more likely 13-14% as a country, and 25-30% for the harder hit areas.
https://covid19-projections.com/us

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amercer
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In reply to beerad12man • 7:05p, 8/13/20
AG
Serological surveys from hard hit areas disagree with that model. However, both could be correct if asymptomatic cases do not result in b-cell immunity.

Still I don't see any good evidence that this is about to burn out.
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beerad12man
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In reply to amercer • 7:08p, 8/13/20
AG
Tons of it if you are looking. If you are being cautious and don't want to see it? To each their own, I guess. All we can do as individuals are form best guess opinions on the data we have

Whats happening in Sweden and even nyc and nj should not be happening with your logic

Remember you don't have to produce antibodies to have had it and be immune and or extremely unlikely to get it again. That seems to be clear with Some studies they've done
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beerad12man
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In reply to amercer • 7:09p, 8/13/20
AG
This would have to have a 2.5% death rate to be at 2%. FWIW

All studies show 0.25% to 0.65%. And even some hypothesize less now that we have better advancements in treatment.
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amercer
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In reply to beerad12man • 7:14p, 8/13/20
AG
Oh I agree that you can find some evidence to support whatever your position is in 2020.

I like all the optimism that you guys post, but like I said on the other thread, that analysis is an outlier.

It will be a long time before we know which models were right and which were bull*****
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beerad12man
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In reply to amercer • 7:16p, 8/13/20
AG
It is not an outlier. Plenty of other data out there too. Plenty of other opinions out there too that are similar
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zachsccr
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8:14p, 8/13/20
AG
Y'all have some REALLY smart 5 year olds
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eric76
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In reply to Ragoo • 9:13p, 8/13/20
AG
Ragoo said:
eric76 said:
beerad12man said:
Covid is a type of cold. It's just a brand new one that they haven't seen before. It's also part of the reason many seem to be somewhat immune to it. Not that they can't get it, but why 30-40% are either asymptomatic, or have minor symptoms. Potentially because they have some kind of immunity from past coronaviruses.

There are a lot better experts out there than me, and I'm sure a few things I've said aren't necessary facts. But I think it's the general idea.
A type of a cold? Really?

Is rabies a type of cold, too? How about polio?

Hint: A cold is a disease of the upper respiratory tract caused by a virus. Covid goes way beyond being a cold.
https://www.cdc.gov/coronavirus/general-information.html
Covid-19 is not the "common human coronavirus" they are talking about on that page.

Yeah, there are some coronaviruses that cause a common cold. Covid-19 is not one of them.

It says as much on the page:
Quote:
This information applies to common human coronaviruses and should not be confused with coronavirus disease 2019 (formerly referred to as 2019 Novel Coronavirus).
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94chem
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9:21p, 8/13/20
Smallpox is a hemorrhagic cold. ALS is just a neurodegenerative cold. All the Soviet premiers died of colds, too.
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Ragoo
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In reply to eric76 • 9:24p, 8/13/20
AG
Only because Covid-19 is not a common human virus.

Over time, who knows how long, this too will be a common human coronavirus.
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amercer
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9:24p, 8/13/20
AG
Polonium colds are especially bad
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eric76
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In reply to Ragoo • 9:37p, 8/13/20
AG
Ragoo said:
Only because Covid-19 is not a common human virus.

Over time, who knows how long, this too will be a common human coronavirus.
It may become common, but it will not be one of the ones the page is talking about.
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Ragoo
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In reply to eric76 • 9:40p, 8/13/20
AG
eric76 said:
Ragoo said:
Only because Covid-19 is not a common human virus.

Over time, who knows how long, this too will be a common human coronavirus.
It may become common, but it will not be one of the ones the page is talking about.
why is that?
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eric76
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In reply to Ragoo • 10:27p, 8/13/20
AG
Ragoo said:
eric76 said:
Ragoo said:
Only because Covid-19 is not a common human virus.

Over time, who knows how long, this too will be a common human coronavirus.
It may become common, but it will not be one of the ones the page is talking about.
why is that?
That page is very explicitly talking about four common coronaviruses that cause colds.

The four common coronaviruses are not referred to as common coronaviruses because they cause colds. They are referred to as common coronaviruses in the article because they are common.

Similarly, they do not cause colds because they are "common coronaviruses".

In other words, they are common coronaviruses and they cause colds. If covid-19 becomes common, then it will be a common coronavirus that doesn't cause a cold.
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plain_o_llama
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In reply to eric76 • 10:22a, 8/14/20
We didn't recognize the existence of Coronaviruses in humans before the 1960s. Some speculate that when they jump to the human population there is good bit of carnage while those that can't handle the virus die and the collective immunity of the rest of population comes to handle it like a "common cold."

This is all speculative but we may be living through a test case that will support or counter the hypothesis. And we might not have to wait too long:



a-brief-history-of-the-coronavirus-family-including-one-pandemic-we-might-have-missed-134556

In 2005, a research group from Belgium postulated that the ancestor of hCoV-OC43 one of the current human coronaviruses responsible for a common cold jumped from cattle to humans, leading to what they described as

Quote:
a pandemic of respiratory disease recorded around 1890 in human history.
The researchers argue that in the second half of the 19th century a highly infectious respiratory disease with a high mortality rate, now known as contagious bovine pleuropneumonia, affected cattle herds around the world. Even though most industrialised countries mounted massive culling operations in the period between 1870 and 1890 and were able to eradicate the disease by the beginning of the 20th century, it is plausible that the culling personnel, animal handlers and farmers could have been exposed to coronavirus-infected bovine respiratory secretions.

Around the same time as this coronavirus jump from cow to human could have taken place, a human epidemic attributed to influenza was spreading around the world. This 1889-1890 pandemic was characterised by a general feeling of illness and discomfort, fever, and pronounced central nervous system symptoms. Strangely, the observed central nervous system symptoms were more pronounced during this epidemic than in other influenza outbreaks.

More than one million fatalities were linked to this pandemic. A significant increase in case fatality with increasing age was reported; this means that, as early findings on COVID-19 would suggest, the elderly were harder hit. Even though modern-day science investigation has linked this epidemic to an H2N2 influenza virus, absolute evidence linking this flu virus to the epidemic was never obtained. This is primarily due to the lack of preserved tissue samples from that period.

So if the influenza virus was not the virus responsible for the 1889-1890 pandemic, could there be another culprit? Since the most recent ancestor of the bovine coronavirus and hCoV-O43 was also traced to about 1890, and hCoV-OC43 is now known to have potential to invade and attack the nervous system, could the 1889-1890 pandemic have been the result of the jump of cow coronaviruses to humans?

If the answer is "yes", the next question is this: could the adaptation and co-evolution in the 130 years since the pandemic explain why CoV-OC43 currently causes only mild cold-like symptoms in humans? How is it that the selfsame virus that killed one million people in the 1890s now causes no more than a few uncomfortable sniffles?

This could possibly be a key case study in herd immunity.
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beerad12man
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In reply to eric76 • 10:55a, 8/14/20
AG
I wasn't trying to downplay it to just say it was a common cold. We all know it's worse than your average cold. I just genuinely thought all coronaviruses were considered types of colds, but after researching a bit, I was wrong there. A particular coronavirus, or rhinovirus, might cause the cold, whereas the sars-cov-2 virus doesn't cause a cold, it causes Covid 19. A different disease. Thanks for pointing that out. But the rest of my points still remain the same.

It's a virus. But it's singular, versus the common cold which can be caused by dozens and dozens of different virus strands. So in reality, we can build up herd immunity and even theoretically eradicate a singular strand of a common cold causing virus, or a single strand of influenza virus, but there will still be many more. That's why I say that herd immunity to the one virus Covid 19 is still theoretically possible, and with some studies that have come out, there is encouraging news regarding that make it very realistic. Only time will tell, but my fingers are crossed that this is all but eliminated in many areas of the globe even before a vaccine since the date of one is unknown, and that a vaccine is only the icing on the cake.

It isn't realistically possible to eliminate all cold strands, or all flu strands just because of the sheer volume of how many there are.
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