Do Vaccines Really Prevent Disease?

This is an interesting chart that tracks the prevalence of various diseases as well as when the vaccine was introduced.  Many people ask me if they should vaccinate their children or not, and the best answer is to research both sides of the story and do what you feel is right for your children or yourself.  

My wife and I chose not to vaccinate our children, but it came from reading many books, talking to multiple doctors, prayer, and a mutual decision.  There may not be a right or wrong answer, but when I see charts like this, it makes me wonder.

What are your thoughts?