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Why is Tetanus Immune Globulin sometimes used with the Tetanus Shot

Tetanus caused by the anaerobic spore-bearing bacterium Clostridium tetani is a life threatening condition. The bacteria enter the body through a wound or abrasion. The spores of Cl. tetani occur in the soil, feces and the dust associated with stables. One of the most common injuries causing tetanus is a penetrating wound caused by a nail.

Once within the body Cl. tetani produces a toxin called tetanospasmin under anaerobic conditions within the body’s tissues. Tetanospasmin is a neurotoxin causing the nerves to fire impulses, which in turn cause severe and painful muscle spasms. Where these muscles control the breathing fatalities occur.

Tetanospasmin is a very powerful toxin and as little as 175 nanograms can kill for a 70-kg person. In the United States, the mortality rate is about 11%. In older patients (over 60 years old), this rate increases to 40%. Worldwide tetanus has an overall mortality rate of about 45%.

Fortunately, an effective vaccine for the prevention of tetanus is available. The vaccine is an inactive form of the tetanus toxin known as tetanus toxoid. As this vaccine is part of the childhood vaccination programs throughout much of the developed world, most cases of tetanus occur in developing countries. About 50% of the global total of cases of tetanus occur in Africa. The vaccination provides protection from the action of the deadly toxin not to the actual bacteria.

In developing countries, the most common form of the disease is neonatal tetanus in babies born to unvaccinated mothers. Neonatal tetanus occurs when a newborn infant catches the bacterium either from the use of non-sterile instruments in cutting the cord or the use of tribal medicines, such as animal dung, on the umbilical stump. However, cases do occur in countries such as the United States usually in unvaccinated older people or in persons who have not maintained their immune status by regular booster vaccinations.

Prior to the introduction of tetanus toxoid vaccinations, the main way to prevent tetanus was the use of tetanus immunoglobin. This serum contains antibodies to tetanus toxin and prevents the toxin from affecting the neurons.

The use of an immunoglobin to provide protection is passive vaccination, while the use of a toxoid to stimulate a person’s immune system is active vaccination. Without repeated booster vaccinations, the immunity to the tetanus toxoid drops below protective levels leaving the patient open to developing tetanus.

When a person presents in the ER with a wound that has a risk of contamination with Cl. tetani a booster vaccination is given. This booster causes them to increase the amount of circulating antibody to the toxin so preventing it from acting on the neurons. For such a booster to work the patient must have had a prior record of tetanus toxoid vaccinations.

When the patient has no record of vaccination then immediate passive vaccination with the tetanus immunoglobin provides protection. A vaccination using tetanus toxoid starts the production of the patient’s own antibodies but this takes time before protective levels are achieved. Tetanus symptoms may appear within 4-14 days and the immune system can take longer before it reaches a protective level. Once the toxin has bound to a neuron it is unaffected by any antitoxin. The use of passive vaccination protects a non-immune subject until his or her own immune system responds to the active vaccination.

The use of tetanus vaccinations both passive and active has saved many lives. Tetanus vaccination is now part of the WHO vaccination program in the hope that the marked decrease in numbers and deaths from tetanus seen in the developed word will be seen in the African countries and other parts of the world where it still causes far too many deaths.

Reference Source:

eMedicine Medscape

eMedicine Health

World Health Organization