
Efficacy refers to how well the intervention works under ideal and controlled conditions. It focuses on whether the intervention can achieve the desired outcome under optimal circumstances. The purpose of assessing efficacy is to determine whether the intervention has the potential to work in real-world settings before evaluating its effectiveness in broader populations. It is mostly measured in Randomized Controlled Trials (RCTs).
Effectiveness refers to how well the intervention works in real-world conditions or everyday clinical practice settings. It also considers factors such as patient diversity, adherence to treatment protocols, and variability in healthcare delivery. Unlike efficacy trials, effectiveness studies are conducted in more diverse and representative populations. Observational studies can be used for effectiveness where researchers observe participants without directly manipulating variables.
Efficiency refers to how well the intervention achieves its results compared to the resources (such as time, money, manpower) used. An intervention can be considered efficient if it produces significant benefits relative to its costs, maximizing the value of resources invested. Assessing the efficiency of interventions is crucial for ensuring that healthcare resources are utilized effectively to improve population health outcomes. A cost-effectiveness study can tell the efficiency in comparing the resources and outcomes.