I received the vaccine at 3 PM Eastern time. It's 6:30 now. I have not had any allergic reactions. I expect to feel lousy tomorrow (to what degree, I don't know) but nothing alarming has occurred, and I think that if I were going to have hives, breathing troubles, etc, it would have started by now. It takes only 30 minutes or less for me to have an allergic reaction if I'm going to.
I'll continue reporting back Saturday and Sunday in case my experience is useful for others contemplating getting this same shot.