Thread by @DavidSteadson

Let's talk about herd immunity.

But first, lets talk about herds.

Here is a herd of cows.

But if you look closely, it's not a herd of cows. It's several herds of cows. I count at least 3, and perhaps 4 or even more.

So what makes these different herds? This thing along here - a fence.

Herds are a group of animals that stick together. The cows in one field aren't all in mingling with the cows in another field. The fence keeps them apart. They're different herds.

So how does herd immunity work? Well imagine ths cow here was not very healthy. Let's call her Auntie Bessy. Now Auntie Bessy has been sick a lot since she was a baby. But she made it through and you still love her and she's a valued member of the herd.

Imagine some nasty disease broke out in the cows up the back. Let's call it Cowsick-19.

Now most of your herd is young and healthy. They'll probably be just fine if they get Cowsick-19. But Bessy? She'll die. You don't want Auntie Bessy to get Cowsick-19.

How can you protect Auntie Bessy? Well, obviously for a start you need to keep her away from all the sick cows on the other side of the fence. Then they can't infect her. But what if one of her herd mates wanders up to the fence and breathes in virus from the sick herd?

That cow, let's call him Bob Cow, wanders back to the herd, and now you have two sick herds. And Auntie Bessy gets sick ... and dies.

But what if Bob Cow is immune? He got the Cowsick-19 back when he was a kid! He wanders up to the sick cows, and he doesn't get infected!

So when he wanders back to Bessy and the rest of the herd, the virus don't come with him. Bessy doesn't get infected! Auntie Bessy is a happy cow.

But what if Jomoo, a cow in the other herd, manages to get through the fence and wander down in to Bessy's herd? Bob Cow might be immune? But the others aren't.

Jomoo now infects the cows next to her, who pass it on to the one's next to them ... who pass it on to Auntie Bessy.

Auntie Bessy gets sick .... and dies.

Imagine instead though, if those others cows were like BobCow, and they were also immune. So when Jomoo wanders down, they don't infected. They never pass it on to Auntie Bessy.

The "herd immunity" protected Bessy. So how do you get to herd immunity? Well, you need a wall of immune cows around Bessy. They can be immune like Bob Cow, for example, who got infected young and his immune system learned to fight the disease.

Or you could vaccinate the cows, essentially tricking the immune system in to thinking it had been infected, so it trains up on how to beat the virus. Poor Aunt Bessy though - she can't be vaccinated due to her "underlying condition", but she's protected by the herd!

Now, it may be of course that JoMoo wandered down and infected Auntie Bessy directly, but we know that if you get enough cows in the herd to be immune from infection, it will stop there, and won't just keep spreading to other animals, who might be vulnerable.

If you reach this "Herd Immunity Threshold", then the virus will die out, rather than infecting everyone, and the vast majority (hopefully all!) of those in your herd that aren't immune will be safe. The immunity wall will protect them.

But what if you don't have the fence? What if all the cows can wander back and forth freely?

Well Auntie Bessy is probably going to get infected. She'll run in to an infected cow sooner or later. In reality, you don't have two herds - you have one herd and the virus will spread.

So right now, countries around the world are talking about getting to "herd immunity" through the widespread infections of Omicron.

So here's a map of the Baltic region. A Swedish herd. A Norwegian herd. A Finnish herd. A Danish herd etc etc.

Or is it? Where are the fences? Are the herd members kept apart, or are they free to mingle?

Here's a picture of Oresund Bridge, a bridge between Sweden and Denmark.

I don't know what the traffic is like at the moment, but prior to the pandemic, millions of people *a month* passed back and forward over that bridge. That's more people than live in the region where the bridge lands in Sweden.

You also have the long Norwegian land border. Borders with Finland. Multiple international airports. Boats coming and going.

*Sweden is not a herd*. It doesn't matter if 90% of Swedes become "immune" if there are constantly millions of people entering and leaving the country.

There will be no "immune wall" to protect the vulnerable. To have a herd, you need a fence

Ironically, many of those who promote a "herd immunity" strategy to combat Covid are critical of countries like New Zealand, who have done one of the things necessary - they built a fence.

So New Zealand might be able to reach herd immunity. *Any country with open borders and large exchange of population cannot*.

It's simply impossible.

It's *also* impossible if members of the herd can still get infected, and pass it on to the vulnerable. There is no immune wall.

So what is it everyone is talking about now when the say "country X" will soon reach herd immunity!

They've redefined it. They've done this in two ways -

1. thrown away the part about it being a strategy to protect the vulnerable

2. they've completely ignored the fact that many people who are vaccinated, and - after 6-12 months (perhaps now even less) - most people who have been infected can still get infected, and still pass the virus on to others.

The virus will *always* have a lot of people who it can infect. Under these circumstances, the virus **will never die out*.

So now, the strategy is not to protect the vulnerable, nor is it to get to a level of immunity that the virus dies out.

*It is not herd immunity*

Now the strategy in the west is to let everyone get infected. The vulnerable? Those who can't (or won't) get vaccinated? They are, essentially, to be allowed to be infected, and if necessary die.

Eventually - the "hope" is - everyone who is at risk of severe illness or death will be infected, and many will die. Everyone else will just get a "mild" version of Covid, with their vaccine and/or infection boosted immune system stopping them getting seriously ill.

That again - everyone who is at risk of severe illness or death is going to left to get infected, and either survive it, or die. There will be little effort to stop this. Healthcare workers - it's up to you, and only you.

That's the plan in Europe, in Australia, in the US

When I said the "hope" is - I really meant it. This "plan" **depends on hope**.

The hope is that the virus won't mutate to be something more deadly.

It's important to emphasise - **there is no scientific basis for believing this will be likely**.

It's possible, sure, but it's essentially down to chance. And every infection we allow is another chance (or thousands actually) to allow the virus to mutate - for good or for bad.

Herd Immunity is not going to happen. It's a lie. As I said back in November, what we see this winter is going to happen every winter (and in many places, other times too) until we either change strategies, or get better vaccines.

Don't fall for hopium. It's a giant pile of...

/end

PS cow experts tell me Bob is apparently trans. I'm fine with that. 👍😁