Scientific challenges for precision public health.

The notion of 'precision' public health has been the subject of much debate, with recent articles coming to its defence following the publication of several papers questioning its value.Critics of precision public health raise the following problems and questionable assumptions: the inherent limits of prediction for individuals; the limits of approaches to prevention that rely on individual agency, in particular the potential for these approaches to widen inequalities; the undue emphasis on the supposed new information contained in individuals' molecules and their 'big data' at the expense of their own preferences for a particular intervention strategy and the diversion of resources and attention from the social determinants of health.In order to refocus some of these criticisms of precision public health as scientific questions, this article outlines some of the challenges when defining risk for individuals; the limitations of current theory and study design for precision public health; and the potential for unintended harms.