I was not vaccinated as a child because my mother thought vaccines were evil, unchristian, and other ridiculous things. This was in the early 80s before all the autism-bs, but she had her own unique theories. I got myself vaccinated when I went to university. My mother was disappointed and wanted to write a letter to the school explaining her religious views on vaccines (as she had done for years to keep me exempt) but I decided to go with science.
The most amusing part was going to doctors trying to get childhood vaccines as an adult. One doctor didn't even believe me. He actually laughed, What do you mean you need an MMR?! The doctor who eventually got me sorted had to look up a schedule and sort of wing it because it is something she had never dealt with before. We had a good laugh. (Though DTAP is no joke. That shit fucking hurts!) My mother was not happy but sort of conceded that getting vaccinated as an adult was less risky than as a baby or whatever.