A tetanus shot is best administered within 24 hours after injury, and it is still effective if given within 48 hours. If not feasible, the injection can be administered within a week. Tetanus is caused by an infection with tetanus bacillus and is usually very severe. The incubation period for tetanus bacillus is about one week, hence, tetanus antitoxin should be administered as soon as possible after injury to prevent infection. If a tetanus antitoxin skin test is positive, tetanus immunoglobulin can be administered for immunologic skin testing. Symptoms of tetanus, when they appear, mainly include trismus, a forced grin, throat swelling, choking, opisthotonus, etc. If not promptly treated, these symptoms can lead to death.