Before a novel medicine can enter the market, its manufacturer must obtain marketing authorization from the competent regulatory authorities. To satisfy the stringent evidentiary requirements imposed by regulators such as the European Medicines Agency (EMA), the US Food and Drug Administration (FDA), and the UK Medicines and Healthcare products Regulatory Agency (MHRA), a company needs to present data derived from clinical trials, which are interventional studies performed in humans. However, such registrational trials usually have important limitations, including their limited sample size, relatively short duration, and low external validity of the outcomes they produce. While they may provide a good indication of how safe the investigational treatment is and how well it works when applied under ideal circumstances (i.e., exactly as intended by its developers), they are not always appropriate predictors of its effects when used by real-life patients.

As a result, uncertainties often remain regarding the safety and effectiveness of new therapies at the time of their regulatory approval. To tackle these uncertainties, additional data are collected in the post-authorization environment. Such data gathered after a therapeutic intervention has been launched onto the market are typically referred to as real-world data (RWD). The evidence that arises from the analysis of RWD is called real-world evidence (RWE). For example, in the European Union, manufacturers of pharmaceutical products are legally obligated to document and report any serious adverse events observed in patients taking their drugs in clinical practice as part of the pharmacovigilance legislation. This real-world safety information allows for the identification of rare severe side effects and the assessment of long-term risks.