When evaluating actions aiming to improve public health, results can be measured as efficacy and effectiveness. It is common to use the terms interchangeably, referring to ability to produce a desired result. In medicine and public health, however, they mean different things. 1/6
Efficacy is what can be achieved under ideal/controlled setting (eg randomised controlled trial). With strict inclusion/exclusion criteria, one can select a homogenous, motivated study population. Interventions and outcomes can be delivered and measured in a controlled way. 2/6
Effectiveness is what can be achieved when the intervention is used in real world setting. Usually, the effects are less than what the efficacy studies indicated. Potential reasons include more heterogenous and less motivated population, lack of follow-up and feedback, etc. 3/6
The efficacy/effectiveness discrepancy can be observed even with use of medications; in real world the effects usually considerably lower than what was observed in the efficacy trials which led to the acceptance of the drug for the condition. This is well understood. 4/6
Changing behaviour more difficult, difference between efficacy/effectiveness can be considerable. It has been a challenge to scale up lifestyle interventions on nutrition+ physical activity which reduce type 2 diabetes risk. In trials marked effects, in real life more modest. 5/6
Some factors affecting effectiveness that need to be considered before action:
Feasibility: the extent the interventions can be delivered;
Reach: how many can be reached?
Fidelity: delivery as planned?
Acceptability: considered agreeable?
Adherence: followed through?
6/6
Feasibility: the extent the interventions can be delivered;
Reach: how many can be reached?
Fidelity: delivery as planned?
Acceptability: considered agreeable?
Adherence: followed through?
6/6
