These spores can lie dormant for many years in the soil or in animal excrement, until they enter the body through wounds that penetrate the skin. Once the bacteria enter the body, they produce a toxin that affects muscle contraction. Worldwide, tetanus kills 50 percent of all those infected.
Mortality is highest among the young, the old and drug abusers.
However, a successful immunization program in the United States has resulted in only 50 to 100 cases reported each year. A fourth injection is given between 15 and 18 months of age. Children should receive their first booster shot between 14 and 16 years of age. The tetanus immunization may produce side effects at the site of the injection, including redness, swelling and pain. Often, the immunized child will run a fever and experience drowsiness and irritability.