I had mine a while ago (second is tomorrow actually). Sore arm for a few days. Felt a bit iffy the day after. Something between a slight hangover/beginning of a flu. Probably placebo. Nothing to write home about.
I include this very exciting story with the hope of this thread not becoming a home for people self-reporting their adverse reactions. Most people will get it, and get on with their lives without much to talk about (and therefore, not talk about it).