Tetanus is a disease also known as lockjaw, that is caused by a bacterial toxin. It is so named because the condition results in convulsions of the muscles, starting with those of the jaw and face. The bacterial poison is called tetanus toxin, or tetanospasmin. An inactivated form of this compound, known as tetanus toxoid, is used as a vaccine for children or adults, along with the vaccines for several other once-common illnesses. A tetanus shot is also used to treat adults every 10 years — to keep their resistance to tetanus active — and on patients with unclean wounds who have not had a tetanus booster shot within the previous 10 years.
The bacterium Clostridium tetani lives in the soil and produces endospores that can enter the tissue of dirty wounds. This is the beginning of tetanus. The bacteria themselves do not cause the affliction, although they multiply within the oxygen-free confines of the tissue. When they die, however, they release tetanus toxin. After activation by proteases, the toxin migrates throughout the nervous system until it reaches the central nervous system (CNS).
Once in the CNS, the muscles become primed to respond to the slightest stimulation. This causes the convulsions and muscle spasms that are characteristic of the disease. Tetanus toxin is very potent. It only takes a small amount of the poison to bring about this effect and kill 30-40% of the people that contract tetanus.
It is possible to induce resistance to tetanus by injecting a modified form of the toxin. The tetanus toxin is treated with heat or formalin to change its structure, so that it can no longer affect the nervous system. The inactivated toxin is now known as tetanus toxoid. It retains enough of its structure that using it for tetanus immunization will induce an immune response and prevent the disease from occurring, if the person becomes infected with the bacteria.
Tetanus toxoid was first developed in the 1920s. It was used to immunize American forces during their service in World War II. Since the vaccine is based on tetanus toxoid and not a live organism, the immune response tends to fade over time. It is important for adults to get booster shots every 10 years to maintain a resistance to tetanus. Recently in the U.S., most cases of tetanus have been found in adults aged 50 years or older.
Immunization with the tetanus toxoid is almost completely effective in inducing resistance to tetanus. If a person has not kept up with their booster shots and contracts tetanus, however, it is possible to die from the disease. It is standard medical practice to treat patients with dirty wounds with a tetanus booster shot, but it takes several weeks for the body to develop antibodies to the toxoid. Tetanus can kill a person in the time it takes for the vaccine to take effect.
Starting with infants six weeks old, children are now strongly recommended to receive immunizations for tetanus, along with several other diseases. The vaccines for these conditions have been developed so that one shot can deliver the substances to cause resistance to multiple diseases, although a series of shots are required. Commonly, tetanus toxoid is combined with the toxoid for diptheria. Also included is the vaccine for pertussis, also known as whooping cough. This vaccine series can also be combined with the vaccines for polio, hepatitis B, and Hib — a form of influenza B.
Side effects of the tetanus toxoid are usually minimal. Adults who get the tetanus toxoid vaccination generally only have localized, non-serious reactions. Symptoms to watch for in children include convulsions, a fever greater than 103°F (39.4°C), vomiting, seizures, or swelling of the glands in the armpits, among others. For children getting the combination vaccines, seizures are extremely rare, and one child per 16,000 exhibits a high fever. The rare fever is thought to be due to the pertussis vaccine, and the child is thought to still have immunity to tetanus and diptheria.