I dont think you even need injury to do it. I think some get systemic after. I had a tetnus shot then a week later had tiredness and joint pain over feet and hands. Which over a month later has not gone away but worsened. I did have strep during that time. But the more i think the more i think the shot had something to do with it. I even think they missed the muscle or something because the injection site got sore the FOLLOWING day and stayed sore for about a week. Needless to say i wont be getting another unless i actually cut myself since they seem now to do it for laceration regardless of past booster.