I was due for my tetanus shot yesterday, which I got, along with a whooping cough shot. My question is, what makes the arm hurt after a shot, the vaccine itself, or the needle stick? Because today, my arm is KILLING me! I can barely lift it from my side. I know they say you might feel tender or get a fever, but I don't remember a shot hurting quite this much before. If it's the needle stick that makes it hurt, I am for sure going to use the smallest needles possible at work when giving intramuscular injections, no question. If my arm hurts this bad, I can't imaging what animals' legs must feel like after an injection!!!