Herd Immunity Discussion

I have been watching, as we near herd immunity, and the infection rates have dropped like a rock, over the past 2 to 4 months. Outside of the US, things look much worse, but every time I look at the real numbers, I see they are just going through the surge we went through last winter.

I recall how, the CDC, the NIH, and other agencies came up with model after model, last March and April, then in May, trying to tell us when the infections would peak and begin a decline. Nothing they told us came out right, as we peaked in May and the infection rates drifted up and down over the summer and into the fall.

Then, as winter set in, the virus surged again, to record heights, but then, once again, it peaked and declined. But everyone wants to know: will there be another surge.

The short answer is no, we shouldn't see another surge.
But not 100% definitely no.
Maybe 98% no.
That is about as good as it gets in epidemiology.

In this thread, I will show the formulas I use, and some of the results. I will show the ideas, some assumptions, and some of the limitations, for those formulas.

If possible, I will also look at the vaccines, the variants and the mutations, and what each of them might bring us.

The numbers are still climbing here. It may only be 5or 10 people per week in our county but it is still going up...

Sigh i will still wear my mask

The original formula:

H=4C+V

C was percentage of people who had recovered from infection, and V is the number of vaccinations given.

This was obviously too simple, but it accounted for the fact that around three quaters of the population never was vulnerable, and gave a general ball park estimate. It is still useful for looking at other countries, where they haven't passed 50% herd immunity.


In April I moved to a More Robust Formula:
I will call it Formula 2, and I do it as  a five step process:

v1 and v2 are % of people having taken first and second shots
a and b are based on % of total population and % of pop over 18yrs.
C is % of people who have had the virus
v2=(v2a+v2b)/2
v1=(v1a+v1b)/2
V=(v1+v2)/2
H=(4C+(V-C/1.33))/1.1
H is percent Herd immunity.

Reasoning
This formula deals with the redundancy of people who get vaccinated after recovering from infection. It gives extra weight to adults who get vaccinated, less weight to younger people. (would be better if I devided the population at age 60 )

Assumptions:
Aproximately 25% of the population is vulnerable to begin with
(I know this is between 15% and 30%, through observation)

Population is aproximately 333Million
(my original estimate, until 30 April, was 323Million)

Infection gives 75% immunity (this is why I divide by 1.33)
Best average immunity from shots and infection 90% (why I divide by 1.1)

You don't need 100% immunity for herd immunity
Infection rate slows as you approach herd immunity,
but never completely goes away.

Limitations:
This formula could eventually go over 100%
Current infection rate seems to indicate less than 25% of population is vulnerable.
If only 22% is vulnerable, need to change "4" in above equation to "4.5"
If only 20% is vulnerable, need to change "4" in above equation to "5"

Dave58 wrote:The numbers are still climbing here. It may only  be 5or 10 people per week in our county but it is still going up...

Sigh i will still wear my mask

Places with higher population density, and places where the virus didn't have as much spread, from June through January, still have a pretty large vulnerable population. Other places, like Florida and Arkansas allowed it to spread in the summer, when the virus would do less damage, and now they are seeing better numbers.

Also, people should be looking at numbers compared to January, not last week. (And the news likes to tell us the total, since this all began, like that number might go down ) A rise of 50% looks really bad, but from 2 infections to 3 is 50%, while a rise from 700 to 707 is 1%. Sounds better, but it is worse.

Some Recent Numbers:

Current Herd Immunity Calc (26 Apr)
C= 9.8%
Fully vaccinated v2=33%
partially vaccinated v1=48%
H=(4C+(V-C/1.33))/1.1
Putting the numbers in gives:
H=(39.2+(40.5-9.8/1.33))/1.1

We passed 65.75% of herd immunity, as a nation.
about 35% due to infections
and about 30% due to vaccinations.

Edit to add:
Census data came out:
C= 9.5% instead of 9.8% based on new population

Dave58 wrote:The numbers are still climbing here. It may only  be 5or 10 people per week in our county but it is still going up...

Sigh i will still wear my mask

I took a look as several states, and can't find any states where the infection rate is rising.

.
Herd Immunity Calculations for 07 June
C=10.0
v2=47.5%
v1=57.6%
H=(40+(52.5-10/1.33))%/1.1
77.3%
about 34% due to infections
and about 43% due to vaccinations

We are making gains.
Variants, in the US, seem to be displacing one another, as primary infecter, but don't seem to be altering our trajectory towards herd immunity. At least not substantially.

We should achieve basic herd immunity in Aug, in most of the US.
(That doesn't mean no cases, but we will be down to a few dozen, here and there, instead of thousands.)

We have made progress to the point where my current formula for herd immunity is not going to be accurate. Plus I have a bundle of new information (I will explain in the next post) that is moving me towards retiring that formula.

The formula shows that some of us have recovered from the virus, some have been fully vaccinated, and some simply will never get it. The remainder, only about 3% or 4% of the population, is still vulnerable. The newest variant, Delta, throws a bit of a wrench into that, by infecting people who have recovered from prior infection, or have been vaccinated.

This means that, in reality, about 15% of us are still somewhat vulnerable, though most of the reinfections will be very mild.

What we don't know is, how many of these reinfections or vaccine breakthrough infections will be contagious.

More on the newest variant: Delta.

It is far more contagious than its predecessors. It will make a lot more people very sick. This does not translate to more people dying.

This is important:
It puts forth completely different symptoms

New symptoms to look for:
Headache, sore throat, runny nose, fever and cough.

This variant does not remove sense of smell or taste.

By the time the symptoms emerge, the damage is done, and the person may have been contagious for several days.

For the science geeks, I will put my full write up in the next post.

I reverse engineered this new "Delta" variant, and here is what I determined.

A new mutation, primarily responsible for the damage the Delta Variant is causing is L452R. This, to me, appears to be an evolution of the E484K mutation. The viruses with L452R mutation are Delta and Kappa, and the major difference between these two seems to be which test finds them.

The success of a virus in an environment that is hostile to it, is primarily dependent on how easily it transmits, not how fast it replicates or how resistant it is to antivirals. This is slightly different from bacteria becoming resistant to antibiotics or mosquitoes becoming resistant to pesticide.

Because of this, every new variant of Covid in the first year simply traded faster replication for easier attachment to a new host. This meant that every new variant infected more people, but the fatality rate was reduced.

The newest variants still follow this rule, except Delta has a new twist. It shows up in new symptoms. Where the older strains attacked the sinus membrane right where the sense of smell was located, and replicated there, the first symptom was loss of smell. This is also common with Rhinovirus, aka the common cold. The newest variants seem to prefer to do their initial replication near the vocal cords, esophagus, tonsils, adenoids and uvula. And because the tissues here are fertile grounds for it, it doesn't enter the bloodstream for several days.

Thus, the Delta variant no longer removes the victims sense of smell. The symptoms to look for are headache, sore throat, runny nose, fever and cough. By the time these symptoms emerge, however, the damage is already underway. The virus has a strong foothold, and the person has been contagious for several days.

Another consequence of this mutation is, while it replicates slower, it gets a "head start" on the body's normal defenses, by incubating where the body isn't looking for it. In a vulnerable person, this means it can damage them severely, causing a rise in hospitalizations and deaths.

Also, in a person with antibodies it can hide until it reaches the stage where it is detectable before the body reacts and kills it off, giving us our higher incidence of reinfections and "vaccine breakthrough" infections.

We do know that the vaccine is still effective, although slightly degraded, what we don't know is, with this new variant, how contagious is a typical "vaccine breakthrough" case.

Let me know if anyone has any questions.

Today, I discovered a flaw in the above analysis. Most of my analysis of the new variants seems to be correct, but I found one part that isn't.

And it is a bit of bad news.

The L452R mutation, which makes the Delta variant a lot different from others is not an evolution of the E484K mutation. It is possible they evolved from the same predecessor, but they took off in different directions. And, what is more, there is a third one that is still different.

The bad news of this is, that if you get one of those three, you are only halfway protected against the other two.

The good news is that if you got the original virus (several weeks ago) or either the phizer or moderna vaccines, you are fairly well protected against all three.

The new information is drawn from here:
https://afludiary.blogspot.com/2021/06/cell-reduced-neutralization-of-sars-cov.html

The last three months have been a cram course in learning about viruses, and about Government and Corporate disinformation campaigns.

Two things I want to touch on here, and I will give more detail in a later posting.

First, some good news: recovering from the virus gives almost total immunity to all known variants.

Second, the vaccine doesn't keep you from getting the virus, but it keeps you from having symptoms, or at least it drastically reduces the symptoms, so you don't get nearly as sick. That is halfway good news.

Agree TRex, but you can still be hospitalized and die from covid even if vaccinated.

Although, the numbers are very small, it still happens.

You are better off, far better off by getting the vaccine, that's a personal choice each of us need to make.

https://www.deseret.com/coronavirus/2021/8/10/22618163/covid-deaths-vaccinated-data-how-many-die

rick1 wrote:Agree TRex, but you can still be hospitalized and die from covid even if vaccinated.
Although, the numbers are very small, it still happens.
You are better off, far better off by getting the vaccine, that's a personal choice each of us need to make.
https://www.deseret.com/coronavirus/2021/8/10/22618163/covid-deaths-vaccinated-data-how-many-die

I agree with everything you said here, for anyone over 50, most people over 30, and anyone of any age with other health issues. I have some reservations about vaccinating young people who are in good health, but that isn't one of the issues I want to address here.

Here are the issues I wanted to address here:

1. The latest surge here seems to be subsiding in most of the Red States. Some of the states with the most stringent masking, and longest economic shutdowns seem to be a little behind us.

2. I may be able to fill in more details later (if anyone has any questions), but for now, I would like to say that there were two errors in my assumptions about this virus that caused my forecasts to be off for this summer surge.

3. One of them was an assumption that a real epidemiologist may have known better. I saw a substantial portion of very blatant exposures result in no illness, not even a positive test. While an infection that tests positive but has no symptoms is known as "asymptomatic," and is still contagious (but to a lesser degree), what is one that never tests positive, but is still slightly transmissible, and results in immunity for the infected person? For lack of a better term, I am going to call it "silent." The silent cases weren't very important in the earlier strains, since they didn't amount to any substantial portion of the population.

4. But, it did create a statistical anomaly. It appeared that nearly 75% of the population was already immune, before the virus arrived. It was only when I saw statistics on how many people had the antibodies (a number that only became available a few weeks ago), that I realized we were dealing with a large number of silent cases. Still not a problem for my forecasting model.

5. But Delta grew that "feature" of the virus into a storm. The silent cases? Some of them became asymptomatic (note 1), and others remained silent, but now they became much more likely to spread, as opposed to earlier variants. That is why a surge that should have been a mere blip grew to 5 times the size I forecast, and lasted twice as long.

6. The other assumption was based on a lie, told to the public, about the vaccine, last winter. Breakthrough infections were supposed to be few and not very contagious. Malarkey. Breakthrough infections, as we know, are quite common, and more so with the Delta variant (nearly universal, as a matter of fact). And very contagious, as well. But almost all of them are asymptomatic, creating a spreading hazard many times worse than expected.

7. And both the pharmaceutical industry and the government knew this, months before they revealed it to the public. They kept it under wraps to prevent "vaccine resistance" among the people who don't trust the government.

8. To put it another way, because they were worried people wouldn't trust the government, the government lied to the people.

9. This is why they had so many mixed messages about wearing a mask, even if you have been vaccinated. Remember especially, when they said if two people are together they need to wear a mask unless both are vaccinated. This exposes that they knew this would be a problem.

10. Another reason these "breakthrough infections" are being lied about is that if people realize the number of asymptomatic breakthrough infections, they will realize it isn't the unvaccinated people who are responsible for the high number of infections, it is the vaccinated people (ones who have not recovered from the virus, itself) who are spreading the virus.

Thus, for the past few months, we have been experiencing an epidemic surge, driven by people who are vaccinated.

Note 1: the virus hides from the immune system, during incubation, allowing it to become testable before the body knows it is there, assuming the test is efficient at spotting the virus.