Herd immunity is an old concept in immunology. It is so simple; however, it’s mind boggling how reasonable people can get it so terribly wrong. Often, these things happen, because general public falls into one of the traps called “Idols of the Mind” which is one of logical fallacies according to Francis Bacon: “There are also Idols formed by the intercourse and association of men with each other, which I call Idols of the Market Place, on account of the commerce and consort of men there. For it is by discourse that men associate, and words are imposed according to the apprehension of the vulgar. And therefore the ill and unfit choice of words wonderfully obstructs the understanding.” In other words, we all use words in a certain meaning which is specific to our trade and people outside that trade, may assign a particular word a meaning which it does not have within that trade. It happens all the time in everyday conversations as well. This leads to misunderstanding, arguments or outfight intellectual hostility.
So, what is Herd Immunity in our trade? I am sorry about the little diversion here, but I must avoid all four Idols of the Mind when delivering complex explanations to the people outside my trade.
Immunity is a concept used to describe inability to contract a disease, but what does that mean?
Case 1: Because pathogens that cause it, are incompatible with your biology. For example, humans cannot get plant diseases such as Dutch Elm disease or Tabaco Mosaic virus. That is somewhat clear.
Case 2: Pathogens are compatible with your biology, but you are not ill. We say, you are immune to it, which does not mean more that that! You are not ill – colloquially – you don’t show any signs of disease. The words begin to matter here.
That means that you have a disease, when you show its symptoms – isn’t it. No… because you MAY have a disease (in a general public meaning of the term) and not show any symptoms. “So how can you say I have it, it if I’m not ill”, you may ask. My answer would be simple – “because you are passing it on others”.
Reasons for which you don’t feel sick can be manifold, but in general it is that you have very few pathogens in your body and they haven’t succeeded to overcome your immune system (system, which prevents and fights diseases), or you might have enough pathogens in your body, but they themselves are too weak to cause damage (yet your body knows about them and is fighting one the less), or you don’t feel sick yet, because believe it or not, microbes need some critical mass to cause disease before it shows, this is called “Incubation period”.
Immunity – inability to get disease can come (Idols of the Marketplace again here) in two forms:
- Innate – you are born with it, so in case of COVID19 this goes out of the window
- Adaptive – without much theory – the one you acquire during your life
Adaptive immunity becomes an important concept in delivering my point about Herd immunity. People around us are therefore immune to variety of conditions:
I am immune to polio, tuberculosis and so on, because I was vaccinated as a child. Let me elaborate just a little bit, so I don’t bore the reader to death with technicalities. You are a castle and microbes are an invading army. You have a castle wall, maybe a moat, a fall bridge, and army inside. Attackers have their siege weapons, shields, bows and arrows and so on. If you have never fought that particular enemy, you might lose the battle. But if I tell you that the opposing red army can be effectively fought off with fire arrows and that your blue army has metal shield and that arrows will not do anything, you have to get creative. The best would be to use strategy of the blue army, using cut out cardboards – just to be safe. Practice as much as possible and hope for the best. When the real army arrives, you are ready to fight them off. That is vaccination.
The little problem is the memory – some armies are so memorable that you’ll never forget them – polio, rubella, mumps. Some armies are remembered but you need some reminder of them – revaccination or booster shots for hepatitis, tetanus, rabies. And some armies change their coats and strategy so much that you simply can not adopt any effective strategy – seasonal flu. But at least in this case, invading army only stays for a few days, does not really destroy anything, will make a little mess, which you have to clean up and then it just moves on – little like pacifist Vikings….
So, now imagine a land full of these castles. Every castle (a person) has something to offer to an invading army (pathogens) and all castles form a nice country (human population). Imagine that nobody educates the county about the red army and so when castles get attacked and lose, invaders get stronger as they steal food, water, maybe even slight strategy change and are able to move on to a next one. Very soon the whole country turns into non-functioning red castles full of robbers.
This is called an epidemic and if other continents get infected, maybe even the whole castle world, we talk about outbreaks and pandemics.
So what can a poor castle do in such cases? You probably guessed it by now. Well, train you castles – but using what, if I have never seen that kind of army before? What instructions am I going to give to the defenders?
Ok, OK…so don’t allow the red army (no pun intended here) to spread by blocking the roads. Yes, it is like wearing masks and respirators, washing your hands, and not meeting, and not coughing into the air. Maybe only few soldiers will try to attack and maybe a castle handles it well and may as well learn something about this new army. We will show such a castle as blues (because it hasn’t lost) but with a red circle (as a siege).
From the pictures above, one can understand, that to be immune against the attack, you must get the information about the army. So, let’s look at our country little later. As the invading army are invaders, they only pillage and soon the pillaged castles stand in ruin. I don’t want to be blatant here, but yes, it means – the person has died. Some castles can be repainted blue after a disaster and they as well will remember the red army.
At last – the victory….! The blue castles will once again re-populate the country.
This time, the ruler decided that such disaster may not happen again and sets-up army training camps across the county which will teach soldiers to fight the red army and maybe even it’s strategic variants. Such well-prepared country is happy and prosperous and because its inhabitants live in wealth and security, they, generation after generation, mock their generals, who tell the people about this big disastrous historical event. But they only get laughter back, because it’s complicated, it is boring and who f-cking even needs this, anyway. And so some parents decide that their children need arts and farts for life and change the academy for the theatre, or some crocked ex-general (Andrew Wakefield) tells them that training of their children is evil, because from million trained 12 got depressed….. Soldiers do not train and castles lose their ability to fight. This does not mean disaster immediately, as long there are enough resistant castles – red army is still trying to attack, but it can not replenish its forces, because there are so many resistant castles, that it can’t find the vulnerable one.
Once we understood this little example, we understood the concepts of herd immunity. The blue castle without the ring is NOT immune to attack per se, it is just freeloading off the immunity of trained castles and we say that the country has herd immunity towards red army. Surely you understand that this only works, if enough castles train their soldiers and that blue castle’s argument that you don’t need to train solders for anything is stupid and short-sighted.
Every disease can be assigned a herd immunity factor, that is what % of population must be vaccinated in order to achieve protection for non-vaccinated people.
If this factor drops, whatever the reason, and there are valid reasons to refuse vaccination (medical ones, not arguments made from religious or self-righteous point of view which are in my view sick), diseases will re-emerge. Scientists have been talking about re-emergence of smallpox and polio for some time and drop in vaccination in the US is expected to bear some unpleasant surprises in the near future.
Herd immunity in case of novel viruses is nonsense propagated by people who don’t understand intricate detail and evolutionary mechanisms, because they tend to fall into traps of Idols of the Marketplace or try to adopt laymen logic on non-laymen concepts (another idol of the mind, this time – Idol of the Tribe).
Herd immunity in case of COVID19 stinks of neo-darwinism and fascistic idea of the survival of “the strongest” and not “the fittest”, and before someone tells me that that was Darwin’s idea – no it wasn’t:”…it is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.”
The reasons why Herd immunity ideas are bad, are simple:
If you want herd immunity, you must acquire immunity in majority of population (I don’t care how YOU understand it, because it is irrelevant – for nature, at least, before someone accuses me of scientific arrogance).
To conclude
- Let natural selection work its course and the emerging new population will be resistant to the disease – because all susceptible individuals are dead (can there be a more fascist idea than that?) . But this is not herd immunity.
- Vaccinate at least 90% of population in order to expose peoples’ immune system to the weakened or dead virus and we can hope for herd immunity.
- Herd immunity cannot by definition be considered a preventive measure, because it is itself just an emergent property (like thinking is emergent property of interconnected neurons)
- Herd immunity is not passed on individuals within the herd, that is nonsense, like fried ice. It is not jumping from people to people – the pathogens are and even when you, yourselves are not sick.
Autor: Michal Fabian
