Learn how the immune system works and how vaccines use immunity to prevent bad illnesses.
How Does the Immune System Work?
But some people get sick when exposed to a virus, whereas others do not. What’s the difference? The difference is the state of the immune system. If in the past you have been exposed to a virus (or even one that is closely related), your body will recognize it and attempt to fight it off. If, however, you have never been exposed to that virus, it will take much longer for your body to recognize it as hostile and mount a defense. The people who haven’t been previously exposed to the virus are more likely to get infected by it, and the illness is more likely to be severe.
Polio and Other Viruses
To illustrate my point, let’s talk about polio--a virus that attacks the nervous system, leading to weakened muscles, paralysis, and possibly even death. Before the polio vaccine was invented, every year in the late summer people would fear that they or their children would contract this virus. But what most people don’t know is that polio hadn’t always been so deadly.
Prior to sewers and sanitation, people were constantly exposed to germs, including polio. That exposure was constant and low-grade, and so everyone had a degree of immunity to it. The advent of sanitation, however, stopped this low-grade exposure, leading to a generation of people without any immunity to the virus. That made the population ripe for epidemics like the ones that happened during the polio outbreaks.
How Do Vaccines Work?
So what’s the solution? Get rid of sewers and sanitation? Do we let people get exposed to deadly diseases so they can build immunity?
The best solution is to expose people to the infectious agent without getting them sick. That is exactly what vaccines are. I tell children (who absolutely hate getting shots), that the reason we give them a shot is to show their body what the bad germs look like, so when the bad germs try to get into their bodies and make them sick, their body will “punch the germ in the nose.”
This helps, but the kids still don’t like getting the shots. Vaccines are a way for your body to be exposed to a virus or bacteria in a way much safer than getting the infection itself. They employ the body’s own natural defenses to do the work.