The three levels of prevention are primary, secondary, and tertiary.
In primary prevention, a disorder is actually prevented from developing. Vaccinations, counseling to change high-risk behaviors, and sometimes chemoprevention are types of primary prevention.
In secondary prevention, disease is detected and treated early, often before symptoms are present, thereby minimizing serious consequences.
Secondary prevention can involve screening programs, such as mammography to detect breast cancer and dual x-ray absorptiometry (DXA) to detect osteoporosis. It can also involve tracking down the sex partners of a person diagnosed with a sexually transmitted disease (contact tracing) and treating these people, if necessary, to minimize spread of the disease.
In tertiary prevention, an existing, usually chronic disease is managed to prevent complications or further damage. For example, tertiary prevention for people with diabetes focuses on control of blood sugar, excellent skin care, frequent examination of the feet, and frequent exercise to prevent heart and blood vessel disease. Tertiary prevention for a person who has had a stroke may involve taking aspirin to prevent a second stroke from occurring.
Tertiary prevention can involve providing supportive and rehabilitative services to prevent deterioration and maximize quality of life, such as rehabilitation from injuries, heart attack, or stroke.
Tertiary prevention also includes preventing complications among people with disabilities, such as preventing pressure sores in those confined to bed.