Based on what I've read, here is my understanding of the link between autism and vaccines: Some people, because of their genetics, have a weak blood-brain barrier. Unlike the rest of your body, your brain has an extra layer of protection. The blood-brain barrier is what protects your brain from whatever stuff (microbes, poison, etc...) in your blood. Many (60%?) vaccines contain aluminum. For most people this isn't much of a problem, the blood brain barrier does a good job of protecting them. In others, too much aluminum gets through. Autistic people have aluminum deposits in their brain. So in conclusion, some vaccines give some people autism. If autism runs in your family, stay away from the vaccines that contain aluminum. The Hep B for example, it comes in three doses each with a considerable amount of aluminum.