Efficacy

Efficacy is the benefit achieved by an intervention under ideal conditions, typically within a randomised controlled trial (RCT). These ‘ideal conditions’ refer to experimental controlled settings where contextual factors (e.g. treatment administration, patient characteristics, and healthcare system characteristics) are rigorously controlled and balanced across study groups through methods like randomisation and blinding. The design of the clinical trial is usually optimised to demonstrate the intervention’s maximal potential benefit. Regulatory authorities primarily focus on the balance of efficacy and harms (adverse events) demonstrated in RCTs, whereas health technology assessment places greater emphasis on effectiveness.