Commentary on the 2015 SPR Standards of Evidence.

We comment on the 2015 Society for Prevention Research standards of evidence document, summarizing major changes from the previous 2005 Standards, and point to ways in which the Standards could be further improved. We endorse important new standards, such as those on testing the causal theory and mechanisms of the intervention, improved trial reporting standards, and added attention to scale-up research and cost analyses. Despite discussion of replication in the new Standards, we are concerned about the lack of stand-alone replication standards, and the deletion of an explicit requirement for replication before an intervention is considered efficacious. Finally, we are deeply concerned about the lack of attention to the unit or level of aggregation of the intervention target. It is a major conceptual oversight. The unit targeted by an intervention (whether a cell, person, organization, community, state, nation) is a fundamental feature shaping intervention theory, research design, data collection, analyses, effect sizes, diffusion possibilities and patterns, and scale-up issues. Future Standards updates should eliminate the implicit assumption in the current text that effective preventive interventions inherently target individual persons.