Pharmacovigilance

Pharmacovigilance is the science and set of practices concerned with detecting, assessing, understanding, and preventing adverse effects or other drug-related problems, most importantly after a drug reaches the market and is used by far larger and more varied populations than any clinical trial analytics program could enroll.

Pharmacovigilance data comes from spontaneous adverse-event reports filed by clinicians and patients, structured electronic health record and claims data, and increasingly real-world evidence studies designed specifically to monitor safety signals over time. Analysts use statistical anomaly detection and disproportionality methods to flag when a drug-event combination is reported more often than would be expected by chance, which generates a "signal" for further investigation — this differs from a clinical trial's adverse-event tracking, which is confined to a much smaller, more closely monitored and typically less diverse study population.

Pharmacovigilance matters because trials, even large ones, can miss rare adverse effects, effects that take years to appear, or effects specific to populations underrepresented in the original study; continuous post-market monitoring is how these get caught. It also informs health economics and outcomes research by updating the real-world safety profile used in value assessments. A well-known pitfall is confusing a statistical signal with proven causation: a disproportionate reporting rate flags something worth investigating, not a confirmed side effect.