Prevention aims at avoiding the onset of diseases or health damages. Should this not be possible, prevention aims at stopping and limiting their progression, both by improving outcome and by avoiding further complications.
It is possible to identify three levels of prevention, according to the purpose.
Primary prevention aims at strengthening those factors that are useful to health and at eliminating those that are responsible for diseases and injuries. Primary prevention interventions are represented, for example, by vaccination, disinfection, disinfestation and health promotion.
Secondary prevention targets early diagnosis (possibly in the preclinical phase) of diseases, in order to interrupt their progression at the onset (e.g. malignant neoplasies' early diagnosis).
An example is represented by health surveillance which consists of evaluating the workers' fitness for work with respect to a specific task by monitoring their health in relation to the risk exposure in the workplace.
Tertiary prevention consists in preventing any complication or permanent sequelae of a progressive pathological state.
As far as Occupational Medicine is concerned, prevention means safeguarding workers' health by means of eliminating occupational risks in order to reduce or stop work injuries or the onset of occupational diseases.