[Research about vulnerable populations: challenges and opportunities].

There is an important gap in health knowledge about vulnerable and hard-to-reach groups. The development of research projects and the implementation of interventions require strategies adapted to the particularities of these groups. This article reviews some of the main issues through the lens of recent projects conducted in French-speaking Switzerland.
Competing Interests: Les auteurs n’ont déclaré aucun conflit d’intérêts en relation avec cet article.