Ask A Scientist

Why do you need to get a Tetanus shot if you’ve already had one?

Asked by: Emma Ospelt
School: St. James Middle School
Grade: 8

Hobbies/Interests: Soccer, softball, shopping
Career Interest: ER doctor or pro-soccer player

Answer from Sally Dear

Adjunct Lecturer, Ph.D. Candidate, Binghamton University

Research area: Family health, birthing rights, mothering
Family: Fiancé Rob; 3 daughters – Georgia (28), Alana (25), and Kaela (22); step-son Cody (23); and granddaughter Hannah (2)
Interests/hobbies: Spending time with family, exercise, riding my motorcycle, reading and writing, cooking

Tetanus is a rare, but often fatal, disease caused by bacteria called Clostridium Tetani.  Tetanus is also called Lockjaw because the most common symptom is a tightening of the jaw muscles caused by spasms or contractions of the jaw muscles and muscles in the neck.  The poisons produced by the bacteria cause these spasms.  There are about 100 cases of tetanus each year in the United States.  One out of three people who get tetanus will die.

Most people think you can only get tetanus from injuries that involve rusty nails or deep puncture wounds.  However in recent years more people have gotten tetanus from minor wounds, probably because more severe wounds were treated properly.  Some people have become infected with tetanus from burns, lacerations, dental infections, animal bites, body piercing, tattooing, and from splinters.

Tetanus spores are most commonly found in the soil and in the intestines and feces of animals and humans.  People can get tetanus if the Clostridium Tetani bacteria enter the body through a break in the skin.  To help prevent the bacteria from getting into your body, you should always wash any cut, animal bite, or other wound with soap and water as soon as possible after the injury occurs and seek medical attention if needed.  This is especially important in the case of animal bites where other diseases, like rabies, might be a concern.    

Vaccination is the common method used to prevent infection with Tetanus since there is no antibiotic treatment or cure available.  Most people are first immunized in childhood.  The vaccination to prevent tetanus is included in the DPT (Diphtheria, Pertussis/Whooping Cough, Tetanus) shot which is usually given in a 3-shot series when babies are 2, 4 and 6 months old.      After childhood, doctors recommend that you get a booster shot every 10 years.  If you suspect that you might have come in contact with the tetanus bacteria, it is recommended that you get another shot on the same day that you got injured or, if that is not possible, within 3 days of the injury if it has been more than 5 years since your last tetanus booster.  This is especially important if the wound is dirty because the bacteria can get ‘trapped’ in the wound once it starts to heal and may begin to multiply quickly. 

You can get a tetanus shot from your doctor’s office or at most local health departments.  You should not get the shot if you have a fever of 101 degrees F (38.3 degrees C) or higher.  If you have been feeling sick you should tell your health care provider before getting the shot. 

You should not get the shot more often than every 5 to 10 years because you could become allergic to the vaccine.  You should also not get the tetanus shot if you have had a previous allergic reaction to it.  Also, people who are allergic to Thimerosal (a mercury derivative that is used as a preservative) should not get the shot.

There are some other problems associated with getting tetanus shots ranging from pain and swelling at the injection site to a more severe inflammatory reaction to the injection hitting and damaging a skin sensory nerve.  While sometimes just taking an anti-inflammatory like Aspirin or Tylenol will help ease the pain, other people have to go see a neurologist to determine the extent of the damage.

Last Updated: 3/1/17