Anything you put in your body can have an adverse reaction. Some people are even allergic to water. The thing with autism is that people who develop it after receiving a vaccine were already carriers for the genes, and were likely to develop it anyways. There is no mechanism within vaccines that can cause autism if the genes aren't present. But a bad reaction to the vaccine could trigger a dormant gene. But so could any sort of trauma. My dad's entire family has the genes for myasthenia gravis and rheumatoid arthritis. But the only person to develop them was my aunt, shortly after getting in a very serious car accident and which resulted in her mom dying in a car accident rushing to see her in the hospital. Trauma can triggerots of dormant things in our body.