Dr. Weil is a homeopathic Doctor who of course will want you to believe that medicine is not the answer by the way
To play devil's advocate...the medical establishment will, of course, want you to believe their way is the only way, too.
I think the truth is somewhere in the middle, personally. Vaccines have done a lot to protect society from outbreaks of dangerous diseases. So has washing our hands after the bathroom and eating clean(up until about 20/30 years ago) food.
They do "protect the herd," as was posted earlier. They do also hurt some people. There are side effects. Some people contract the disease the vaccine was meant to prevent or have an allergic reaction to an ingredient in the vaccine.
I think the biggest risk is irresponsible doctors. When you take a vaccine, you're not just getting a small culture of the cells you want to be immune against. There are also other viruses and bacteria in there, along with trace amounts of heavy metals. These are basically byproducts of the methods used to create vaccines. The other viruses and bacteria are forms that were present in the orginal host of the vaccine, for instance. Now...when you take a few of these shots a year, especially in an adult, This stuff doesn't add up to an amount that will hurt you. In my mind...the jury is still out on these cases of sick kids after they've taken several vaccines in a short period of time.
I see the need for them, but it's a case of the needs of the many outweighing the few. They definitely do hurt some people. There are definately some mistakes made in the kneejerk reactions to give so many so quickly to children in some states/school districts and by the doctors that recommended them.