I frequently encounter anti-vaccers who argue that vaccines are bad because they are “unnatural” and “bypass the natural immune system.”
This argument is nothing more than an appeal to nature fallacy. Whether or not something is natural has no bearing on whether or not it is safe and beneficial, so I could stop right here, but let’s look at this argument further, because the core premise of this argument is not even true.
Vaccines don’t “bypass” the immune system, if they did, they wouldn’t work. Rather, vaccines train your immune system to recognize deadly pathogens before you are exposed to them.
Before I can explain how vaccines train your immune system, you need to understand the basic concepts of how your immune system works.
It can be broken into two broad categories: the innate immune system and adaptive immune system. Your innate immune system is, well, innate. It’s always there acting as your first line of defense.
It includes things like your skin (which acts as a barrier to pathogens), mucosal surfaces, and non-specific immune cells like phagocytes and macrophages. That last qualifier is particularly important: the innate immune system is non-specific.
It targets anything that does not belong in your body, but it is not specialized for particular pathogens. Think of it like your basic infantry. It’s a vital part of the military, but for particularly dangerous threats, you often need more specialized troops and weapons. This is where the adaptive immune system comes into play.
The adaptive immune system (aka acquired immune system) provides a targeted response that is specific for a given pathogen.
You see, your immune system uses tiny molecules on the surfaces of cells to recognize friend (your body’s cells) from foe (foreign pathogens). These molecules, known as antigens, are specific for each type of cell, and your body can use them to engineer specialized cells that are specifically intended to fight a particular pathogen.
Thus, when your body detects the presence of a novel pathogen (via its antigens), it triggers the adaptive immune system and begins producing B and T cells that are specific for that pathogen. Think of them like your special ops, snipers, stealth bombers, etc.
The catch is that because the adaptive immune system produces cells that are specific for a given threat, it can’t start producing those cells until your body has encountered the threat, and by that point, your body has already been invaded.
In other words, it takes time for your body to mount an adaptive immune response, learn to recognize and target the invading pathogen, and produce sufficient numbers of the specialized cells.
Meanwhile, despite the best efforts of your innate immune system, the enemy pathogens are replicating, spreading, and amassing a formidable army.
Thus, for highly pathogenic diseases, by the time that your adaptive immune system is ready to go, the invaders have already claimed territories and your immune system is going to war, resulting in you being sick and potentially dying.
If you win the war and survive, your body will remember the disease and keep low levels of specialized troops circulating (via memory B and T cells). That way, a specialized force is ready to go if you are ever re-invaded by that pathogen in the future.
This is what we know as “natural immunity.” It’s not perfect, and it can wear off overtime if your body stops producing and maintaining those specialized cells, but, combined with your innate immune system, it does a pretty good job of protecting you.
So, now that you understand the broad strokes of how your immune system works (it’s obviously far more detailed than what I explained), let’s talk about how vaccines fit into this.
Vaccines present your body with the antigens of a given pathogen (usually via a dead or weakened form of the pathogen), along with an adjuvant to stimulate your immune system.
This causes your adaptive immune system to mount a response even though you aren’t actually under attack. Thus, your body produces the specialized cells for fighting a given disease even though you don’t have the disease. Think of vaccines like scouting reports from spies that inform generals about the enemy’s plans and movements before the enemy attacks, thus allowing them to plan an appropriate defense.
That is fundamentally what a vaccine does. It trains your adaptive immune system to be ready to fight a disease before you actually encounter the disease.
Further, following a vaccination, your body will continue to maintain a reserve of the specialized troops, just like it does after an actual infection. This is what actually protects you from diseases.
It’s not the vaccine itself that protects you. Rather, it is the immune cells that the vaccine stimulates your body to produce (along with the antibodies some of those cells produce).
Like natural immunity, the immunity from vaccines can wear off overtime, but a simple booster shoot will remind your body that this pathogen is important and cause it to continue to maintain adaptive immune cells that are ready to rapidly divide and fight the pathogen as soon as it enters your body.
Thus, as you can hopefully now see, vaccines don’t “bypass your natural immune system.” Rather, they stimulate your immune system and train it to recognize and fight pathogens before you are exposed to them.
Indeed, they work exactly like “natural immunity” with only one important difference: natural immunity requires you to get the disease, whereas vaccines train
Suggested further viewing
If you want an excellent and much more detailed overview of the immune system, Hank Green’s three part Crash Course video series is about the best 30-minute introduction you could ever hope for.