Diphtheria

The diphtheria vaccine consists of a small amount of the toxin that has been altered so as not to cause toxic effects. The vaccine works by prompting the body's immune system to make antitoxin against the altered vaccine toxin. The diphtheria toxin is combined with the tetanus toxin and the pertussis (whooping cough) toxin in one vaccine, abbreviated DPT. The DPT is given in four doses. In the United States, infants are given their first DPT dose at about six to eight weeks of age. If all four doses are administered before age four, the child should have a DPT "booster" before beginning kindergarten. This shot "boosts" the immunity to the disease.

A person can be tested for their immunity to diphtheria by the Schick test, which demonstrates the presence of antitoxin within the body. In this test, a small amount of diphtheria toxin is placed under the skin of the forearm. If the site develops a reaction—such as redness or swelling—the person has not developed the antitoxin from a previous infection or a vaccine, and is therefore susceptible to diphtheria. If no reaction is present, the person had already developed the antitoxin. The Schick test is useful for adults who cannot find their immunization records or cannot remember if they had diphtheria in childhood.