I had a tetanus shot 2 days ago. When I woke up today my arm was red & sore. I called the ER that gave me the shot. They said some people have this type of reaction and to come in if I was concerned. I just thought it was strange it started 2 days later? I think I am going to pass on the ER unless it gets worse. As a student, I have always had all my shots up to date and I have never had this type of reaction before. I will write back with information if I go to the ER.