Why are there Some Illnesses that We Cannot Get Twice?
When people have had smallpox or measles or scarlet fever once, they seldom suffer from them again, even if there should be an epidemic all around them. In some way or other the tissues of the body have become changed as the result of the first attack, and are better able to resist that particular kind of infection. We say then that the body is immune to that disease. Doctors make use of this immunizing power of the body, in a very wonderful way. They can give us a very mild form of a disease, or of a similar disease, by vaccination, and after that we are safe for years from any danger of getting the disease itself. For example, vaccination protects us from smallpox. People are often vaccinated against typhoid and other illnesses; they are inoculated with the actual disease germs, which have been killed or weakened to the point where they are no longer dangerous. To inoculate simply means to introduce into the body disease germs or their products.
Sometimes, instead of actual disease germs, a person is inoculated with blood serum of an animal that has been given a disease and has created in its blood “antibodies” that fought and killed the disease bacteria, or anti-toxins that rendered harmless the poisons produced by the bacteria.
Diphtheria anti-toxin belongs to this class of medicine that prevents disease or, if given in the early stages, cures it.
