Example: When you get the cold, your body inspects it. It realizes it hasn't seen that germ before, and responds by making special proteins to fight off the cold. This process isn't fast enough to stop the common cold, but it is fast enough to make you get well again.
Scenario: Next year, you get a vaccine for the stomach flu. You notice the doctor says to you that it injects the same germ into you. You ask why, and she responds that, "If we put this dead germ into you, then your body will recognize it. Just like it did when you got it last year. It will ahead of time make proteins to fight off the stomach flu. It will remember it forever." So when the stomach flu tries to sneak into your immune system, your body will already know how to fight it off-because the vaccine showed the body what the virus was, and what it was made of.
Apply: It's like a job interview. The vaccine is the person, presenting what they are and what they are capable of. The body is the boss, taking note of this. They will hire you--just like how the body lets it in. And turns out this job isn't for you. Similar to how the body will figure out the virus is foreign and bad. The boss will then know that people similar to you, wont work in this job field. Just like the body will make proteins and remember that that virus is bad.
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I hope this helped! Don't be afraid to mark it wrong if it didn't! || much love!! <33