Oh, and some people can't take the vaccine and or the vaccine is not effective for them. People with organ transplants for instance have to take immune system blockers for the rest of their life after the transplant and the vaccine is not effective for them.
So you're taking a chance that affects more than just yourself.
How can a vaccine hurt you? If you're allergic to ingredients in the vaccine you can have a reaction which will most likely take place shortly after it is administered. If you hang out for the 15min they tell you to after the vaccine then there will be help immediately and you'll almost definitely be okay. You can have a severe reaction as your immune system responds to the vaccine. Usually not too big a deal.
What do people think a vaccine is going to do to them? The actual vaccine ingredients are in your body for a very short time, like a couple days. Then it's just your body's natural immune system working the way it is supposed to building up an immunity to a disease. It's like the most natural kind of medicine I can imagine taking.