Pharmacovigilance has been defined by the World Health Organization as the science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other medicine-related problem.
Pharmacovigilance is often the only means by which to detect rare adverse reactions. Healthcare professionals should be made aware of the importance of the first five years after the marketing of a medicinal product. In clinical trials the medicinal product is used by a limited population. When marketed the product is used by a much larger and more diverse population and that is when rare adverse reactions are often detected.
Pharmacovigilance involves patients, healthcare professionals, regulators and the pharmaceutical industry.