DPT is a vaccine designed to immunize against diphtheria, pertussis, and tetanus.

Diphtheria is a very serious bacterial disease that can make a person unable to breathe, cause paralysis, or even heart failure. Before the DPT shot was introduced, 17,000 children died in a single year in the United States in a diphtheria epidemic. Moderate reactions to the DPT vaccine occur in 0.1% to 1.0% of children and include ongoing crying (for three hours or more), a high fever (up to 105 degrees F), and an unusual, high-pitched crying. Severe problems from the DPT immunization happen very rarely. These include a serious allergic reaction, a prolonged seizure, a decrease in consciousness, lasting brain disease, or even death. These severe neurologic events occur after approximately 1 in 140,000 doses of the DPT vaccine (0.0007%) Most of the reactions to DPT injection are thought to be from the pertussis component.