Herd Immunity Impossible?

[ugimports]

I keep hearing about how we're getting closer to Herd Immunity for Covid-19. Some examples:

https://www.aamc.org/news-insights/herd-immunity-closer-we-think

https://www.muhealth.org/our-stories/covid-19-vaccine-key-reaching-herd-immunity

https://www.avera.org/balance/infectious-disease/why-covid-19-herd-immunity-is-important/

However, the definition is this from here: https://www.mayoclinic.org/diseases-...s/art-20486808

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.

But we're also told that those that get vaccinated can still get and spread Covid, but that the effects on them would be less severe if the receive the vaccine.

https://www.health.harvard.edu/blog/fully-vaccinated-against-covid-19-so-what-can-you-safely-do-2021032522230

Although it’s possible that people who are fully vaccinated could still spread the virus, the vaccines are excellent at protecting you from severe illness, hospitalization, and death due to COVID-19.

https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/covid-19-vaccine-what-you-need-to-know

Also, while the vaccine may prevent you from getting sick, it is unknown at this time if you can still carry and transmit the virus to others. That is why, until more is understood about how well the vaccine works, continuing with precautions such as mask-wearing and physical distancing will be important.

So, if vaccinated folks could still get and spread the virus, what Herd Immunity is being referred to? Is it because the thought is that the number of vaccinated people that can spread the virus is a significantly small number of those actually vaccinated?

[as_rocketman]

The problem is binary thinking. You can't apply population statistics to any single individual.

For instance, suppose the virus usually has a basic replication constant R of 4. That means, on average, any one person who has it will give it to four other people, provided no one has any immunity.

Now we suppose that some people are immunized. To make it simple, for now assume that anyone immunized will definitely not get the virus. So given our test case, where one ideal carrier exposes four ideal candidates, some of them will just not get it. If we immunize three out of four people, then our one carrier will expose four people but only infect one on average, meaning the virus now has an effective replication constant of 1 -- steady-state. Any higher immune resistance and it will gradually die out.

This equilibrium point is what is referred to as "herd immunity," and in these absurdly simple terms it happens at an immunized fraction:

I = 1 - (1 / R) = 1 - (1 / 4) = 3 / 4 = 75%

So now let's get a little closer to reality. In reality (1) not everyone exposed is infected; (2) not everyone immunized gets effective immunity; and (3) those immunized but infected can also infect others. These all happen at different rates, but we can combine them.

In our second model, suppose an infected person with no immunity can expose up to 10 others, while an infected person who is immunized only exposes 2 others. Of those exposed, unprotected people will be infected 50% of the time, while immunized people will be infected 10% of the time. Again, let I be the fraction of immunized people. We can set up a single transaction like this:

Newly infected = Old infected * rate of exposure * rate of susceptibility

NI = ((1 - I) * 10 + I * 2)) * ((1 - I) * 0.5 + I * 0.1))

NI = (10 - 8 I) * (0.5 - 0.4 I) = 5 - 8 I + 3.2 I^2

... and the critical number happens when Newly Infected = 1, i.e., one new infection on average for every one already infected:

1 = 5 - 8 I + 3.2 I^2, giving us

I = 69%

Every little bit helps. Even cheesy cloth masks have some impact.

In real reality, of course, there are very many individual factors. People are not a single herd, but a superposition of many herds. The environment has a huge, time-varying impact, as does our health and especially our behavior.

[Den60]

Given the way these types of viruses mutate, I don't think we will ever have complete immunity. If you get a cold or the flu that doesn't prevent you from getting it again. Your immunity isn't the same as that you get from measles, mumps, chickenpox or via vaccination for polio. Hell, even having chickenpox puts you at risk of shingles later in life. The issue will be whether or not this virus's mutations will weaken it sufficiently to not be as big an issue with the elderly and infirm - though I suspect that many elderly with comorbidities who died with COVID would not have survived the common flu either.

[Scota4570]

Of course we will achieve herd immunity and the virus will go away. IT has happened with every flu type virus that ever existed. To believe this one is magical and will behave differently is just silly.

[TrappedinCalifornia]

Given the way these types of viruses mutate, I don't think we will never have complete immunity. If you get a cold or the flu that doesn't prevent you from getting it again. Your immunity isn't the same as that you get from measles, mumps, chickenpox or via vaccination for polio. Hell, even having chickenpox puts you at risk of shingles later in life. The issue will be whether or not this virus's mutations will weaken it sufficiently to not be as big an issue with the elderly and infirm - though I suspect that many elderly with comorbidities who died with COVID would not have survived the common flu either.

^^^ This is the most likely scenario as we currently understand the virus or, more accurately, as we are told the understanding exists.

Remember, we're only a little over a year into this thing. It's a relative of the flu/cold virus. How long have we been seeking "heard immunity" to those?

The reality is that when you have 7.8 billion, unique members of the 'herd,' you are left with myriad possibilities and potentialities...

...In real reality, of course, there are very many individual factors. People are not a single herd, but a superposition of many herds. The environment has a huge, time-varying impact, as does our health and especially our behavior.

This is particularly true when it comes to the United States. We aren't simply a 'herd within the herd.' We have representative samples from virtually every part of the universal herd. Now, add in our unique culture of individual freedoms/liberties. The result? We have the potential to see/experience many/most of the possibilities and potentialities.

So... Is true herd immunity...

• Impossible? Maybe.
• Unlikely? Probably.
• Attainable at this 'early' a point in the viruses evolution? Not likely.
• Possible? I'm more in the camp of herd resistance (rather than immunity) being achievable, at least for now.

[tsmithson]

[bohoki]

its one of those situations that can only be claimed after it happens there is no set number or percentage it just happens when there are no new infections and when life gets back to normal

[ugimports]

https://thehill.com/policy/healthcare/public-global-health/551423-experts-reach-consensus-that-herd-immunity-is-unlikely

Anthony Fauci, the nation's top infectious diseases expert and President Biden's chief medical adviser, acknowledged a shift in thinking by experts who had once believed achieving herd immunity by summer was a possibility.

“People were getting confused and thinking you’re never going to get the infections down until you reach this mystical level of herd immunity, whatever that number is,” Fauci said to the Times, adding this was why he had stopped using the term "herd immunity."

Looks like the media is waking up and now saying herd immunity (however defined) is unlikely.

[stonefly-2]

Given the way these types of viruses mutate, I don't think we will ever have complete immunity. If you get a cold or the flu that doesn't prevent you from getting it again. Your immunity isn't the same as that you get from measles, mumps, chickenpox or via vaccination for polio. Hell, even having chickenpox puts you at risk of shingles later in life. The issue will be whether or not this virus's mutations will weaken it sufficiently to not be as big an issue with the elderly and infirm - though I suspect that many elderly with comorbidities who died with COVID would not have survived the common flu either.

The "mutations" identified so far as I understand it differ from the original in that they are slightly more contagious.

No reason to think they would respond differently to treatment according to one of the expert's videos we saw here. (forget which)

[Scota4570]

Complete immunity, like we will not see any new cases? That will not happen.

Insufficient numbers of hospitalized cases and deaths as to not justify restrictions on the economy and individuals? That is here now. That is what matters.

With other flu types they never completely go away. We should not expect that now. Demanding the impossible, to justify totalitarian restrictions is simply unelected bureaucrats seizing power.

April 2020, saw about 700 deaths per week
April 2021, saw about 700 deaths per week
January 2021 saw about 3300 deaths per week

The current rate will be about 30K per year. That is a normal flu year.

https://covid.cdc.gov/covid-data-tracke r/#trends_dailytrendscases

This "pandemic" is over. We may see a bump in July-August in the South. I do not care. Time to move on. We can not allow the fear of the flu to control us.

[theLBC]

according to a study in qatar, prior infection is much better than the vaccine.

[therealnickb]

according to a study in qatar, prior infection is much better than the vaccine.

[theLBC]

look at these liars!

[UCT]

Herd immunity isn't going to happen. There are too many things going against it. Non-sterilizing vaccine. Mutations that increase infectivity. Open border bringing in new cases. Not as effective in obese, etc. etc. etc. The chance for herd immunity is just a sales pitch to get people to vaccinate.

[stonefly-2]

The "mutations" identified so far as I understand it differ from the original in that they are slightly more contagious.

No reason to think they would respond differently to treatment according to one of the expert's videos we saw here. (forget which)

Edit: found this researchers vid and he touches on the variants @ 8:14

https://www.youtube.com/watch?v=8XCY...ature=emb_logo,

the rest of the vid is golden as well.