[Efficacy and effectiveness of prevention programs in the population: for a more rational choice of public health...

Evidence Based Prevention is becoming increasingly important to guide the policy-makers to choose preventive interventions to be offered to the population. Sometimes however the impact of an intervention in real conditions (effectiveness) may be smaller than the efficacy estimated in studies conducted in experimental settings. This can be due for example to suboptimal coverage of the intervention or to poor compliance of the involved subjects. Regrettably, this aspect is rarely taken into account in the planning of preventive interventions. To evaluate the discrepancy between efficacy and effectiveness of prevention programs we used as examples two interventions for smoking cessation currently available in Italy: 1) Interventions offered by Smoking Cessation Centers; 2) "Minimal Advice" provided by family doctors.

Using epidemiological data we estimated the expected effectiveness of interventions under different scenarios.

Even assuming that Smoking Cessation Centers always offer the best available intervention (efficacy: 82%), they do not seem able to have a major effect on smoking cessation in the population (effectiveness: 0.8%). This is due to the very small number of smokers that seek help to these centers (1%). On the contrary, interventions based on minimal advice are anticipated to have much higher effectiveness (21%).

Evidence of efficacy of an intervention is not sufficient to ensure that this will have a significant impact on health. The decision to implement a preventive action should be preceded by a careful evaluation of the expected effectiveness and be followed by a post-implementation monitoring to estimate the real impact of the intervention.