The tetanus shot causes slight pain. The injection site is in the muscle of the buttocks, where the pain is mild and tolerable. The purpose of the tetanus shot is to prevent infection by the tetanus bacillus, which tends to thrive in anaerobic conditions and in heavily contaminated wounds, such as those with soil and rust. Therefore, patients with deep wounds contaminated with soil or rust must receive anti-tetanus treatment. Additionally, it is important to promptly treat and dress wounds to prevent infection by the tetanus bacillus and to prevent wound infection. The pain from the tetanus shot is minor.