the only time I was ever hesitant about a vaccine was the smallpox vaccine that they brought out just as I was enlisting. It was widly reported that it was risky to take, as it contained actual virus, rather than just the recognition bits.
In retrospect, I have no idea if the reporting was accurate, misinformed, or fearmongering. But at the time, it worried me.
Also, that whole thing is nonsense of the highest order.