If illness is a battle for your body, vaccines are the war games. By injecting a "lite" version of the virus into your bloodstream, you introduce your body’s defenses to a potential invader – and give it the chance to figure out a quick and lethal response.
This time of year, you’re either happy that you got your flu shot or are regretting not getting one. Yeah, the thought of being injected with a disease is kind of icky, but definitely not as icky as getting sick. In fact, the process that the vaccine kicks off in your body is fascinating, like a giant system-wide war against malevolent invaders.
Every cell in your body wears a molecular “uniform” that is unique to you. Every blood cell, every bacteria, every everything that belongs inside you on a full-time basis. If something comes along wearing a different uniform, that is your body’s cue to attack.
Your frontline is your white blood cells, namely the macrophages, whose job it is to engulf and devour anything that doesn’t belong. Then you have your lymphocytes, which are your special weapons and communications experts – they produce antibodies which are your infantrymen.
As the vaccine needle penetrates your skin, a disabled version of the virus enters your bloodstream. The virus in the vaccine has been altered to be underactive and unable to reproduce efficiently, so it’s like a training exercise for your body’s defense system.
As the vaccine enters your blood, the macrophages immediately recognize the strange uniform and begin to eat the invaders. They digest most of the virus, but they save the “uniform”, which they take to the lymph nodes – cells there receive and analyze the uniform and display it so other cells can “see” it. In essence, saying, “Keep an eye out for these guys”.
Time to Get Medieval
The fun really begins when the lymphocytes come out to play. A type of lymphocyte called a T cell plays on either offense or defense – the offensive team, having seen the virus’s uniform, goes out scouting for any cells that might be harboring the virus and destroys them. Don’t worry, you can make more. The defensive T cells are the communications experts – they send out signals to your other immune system cells telling them where the viruses are and how to stop them. They call offensive T cells into action and also recruit other lymphocytes called B cells.
Search and Destroy
The B cells produce antibodies, which hunt down individual viruses that are circulating in the blood or hiding in nooks and crannies (because the T cells are taking care of the viruses already inside cells). The antibodies stick to the surface of the virus and secrete a sticky coating that renders the virus inoperable, killing the invading force one by one. Brutal.
With all this killing going on, your viral load is falling fast – fast enough that the virus, which has been altered to do this, hasn’t had much time to reproduce. So the infection ends before it ever has a chance to take hold. Once the war is over, some of the lymphocytes leave active duty and enter the reserves as memory cells, retaining the memory of the virus uniform.
The Real Thing
When you do come into contact with the flu (or whatever you were vaccinated against), your little army immediately recognizes the uniform and knows exactly how to defeat it. The memory cells report for duty and spill all their information about an effective defense to the rest of your immune system, and the rest is history.
Your first run-in with the virus (the vaccine) was only easy because the virus was specifically altered to be a cakewalk. Had you not been vaccinated, it would have taken your body longer to figure out just what sort of antibodies to produce and what sort of chemicals to use to kill the invader. So while you would have triumphed eventually, you would probably be pretty miserable for a few days while the battle raged on. But practice runs in the form of vaccines help your body sort things out and get prepared for the real deal.