Tertiary prevention refers to preventive measures at three stages before, during and after the onset of a disease, and the concept of tertiary prevention is conducive to disease control. 1. The first level of prevention is etiologic prevention. It refers to the prevention of diseases before the onset of the disease by reducing the pathogenic factors of the disease and avoiding the causes of the disease. For example, vaccination against the new coronary pneumonia vaccine can significantly reduce the chance of infection and alleviate post-infection symptoms. 2. The second level of prevention is also known as three early prevention, i.e. early detection, early diagnosis and early treatment. Early detection and diagnosis of diseases at the early stage of disease development and appropriate treatment can effectively slow down the progress of the disease, or even cure it after treatment. 3. Tertiary prevention refers to the early treatment and intervention for patients with diagnosed diseases to prevent the deterioration of their conditions, reduce complications and disabilities, and promote the improvement of the disease and functional recovery; and functional exercise and rehabilitation for those who are prone to disabilities, so that they can recover and retain their functions as much as possible. Tertiary prevention is a multidisciplinary concept in epidemiology, preventive medicine and other disciplines, and the concept is conducive to the prevention and treatment of disease.