TABLE 1—

Different Types of Studies Aimed at Evaluating the Impact of an Intervention, With Emphasis on the Dose of the Intervention That Reaches Program Recipients

Type of Study	Units of Treatment	Delivery Mechanism for Intervention	Compliance With Agent by Recipients	Comments
A. Clinical efficacy trials	Individuals	Ideal	Ideal	Classical clinical trials of drugs, vaccines, etc.
B. Public health regimen efficacy	Clusters of individualsa	Ideal	Ideal	Same as above, but delivered to clusters rather than individuals
C. Public health delivery efficacy	Clusters of individuals	Ideal	Best practice	Ideal delivery is ensured, and compliance is actively promoted according to best practice
D. Public health program efficacy	Clusters of individuals	Best practice	Best practice	Randomized allocation of geographical areas to best practice implementation
E. Public health program effectiveness	Clusters of individuals	Routine	Routine	Randomized allocation of geographic areas to routine implementation

^aFor example, geographically defined administrative units, or catchment areas of health facilities.