How does immunity work?
You get sick when germs invade your body. When measles virus enters your body it gives you measles. Whooping cough bacteria cause whooping cough. And so on. It is the job of your immune system to protect you from these germs. Here’s how it works:Germs enter your body and start to reproduce. Your immune system recognizes these germs as invaders from outside your body and responds by making proteins called antibodies. Antibodies have two jobs. The first is to help destroy the germs that are making you sick. Because the germs have a head start, you will already be sick by the time your immune system has produced enough antibodies to destroy them. But by eliminating the attacking germs, antibodies help you to get well. Now the antibodies start doing their second job. They remain in your bloodstream, guarding you against future infections. If the same germs ever try to infect you again — even after many years — these antibodies will come to your defense. Only now they can destroy the germs
