I had the same problem with my daughter. I explained what they were going to do, I told her it would feel like a pinch, then I gave her a little pinch on the arm and told her that was all there was to it. Next I promised ice cream if we could get it done with no screaming. When we went in for the shot I held her on my lap and told her I was going to hug her so she wouldn't be scared. It worked for her.