A toxoid is a bacterial toxin which has been treated so that it is not dangerous, but it retains the properties which trigger the formation of antibodies when organisms are exposed to the toxoid. Toxoids are used in vaccinations which are designed to help people form antibodies so that they can resist bacterial infections. Periodically, boosters of these vaccines must be given to ensure that people will retain enough antibodies in their systems to fight back when harmful bacteria enter the body.
There are several different ways in which a toxoid can be produced. One method involves using heat which weakens or suppresses the toxicity of a bacterial toxin. Another method uses a chemical, such as formalin, for the same effect. Both are done in labs which are subject to quality controls. During testing to confirm quality, technicians check to make sure that the bacterial toxin has truly been weakened so that people will not get sick when the toxoid is used in vaccinations.
Without toxoids, people would have to be inoculated with exposure to trace amounts of bacterial toxins. This could be dangerous, and mistakes may be made which could lead to complications, including death from exposure to bacterial toxins. Toxoids are much safer and easier to use. The dosage does not have to be as precise because a small overage will not result in sickness for the person being inoculated. Toxoids are also safer to handle and transport for health care workers. Both diphtheria and tetanus vaccines are made with toxoids.
When a toxoid is introduced into the body, even though it is weakened, the body recognizes that it is hostile, and the body forms antibodies. These antibodies will remain behind even after the toxoid is expressed, allowing the body to recognize the bacteria associated with the toxoid if it enters the body. When the antibodies activate, the body attacks the bacteria, eliminating them and hopefully avoiding serious complications of bacterial infection by wiping out the bacteria before they can fully colonize the body.
Booster recommendations vary. As a general rule, people are often encouraged to get a booster when there is a chance that they have been exposed to dangerous bacteria. For example, people with puncture wounds may get a booster of the tetanus toxoid vaccine. It is important to keep vaccination records to keep track of when vaccines were received so that people know when they need boosters to keep up their immunity. For adults, a combined tetanus and diphtheria booster is recommended every decade.