Background
The concept ’vulnerability’ is prevalent in the public domain, health care, social institutions and multidisciplinary research. Conceptual heterogeneity is present, hampering the creation of a common evidence-base of research achievements and successful policies. Recently an international expert group combined a specific literature review with a 2-stage Delphi procedure, arriving at a seemingly universal concept of vulnerability for the elderly with applications for research instruments. We replicated and extended this study, to generalize this result to health in general, and perinatal health in particular.

Methods
Two independent expert panels (general health, perinatal health) repeated the Delphi-procedure, using an extended and updated literature review to derive statements on the concept and defining pathways of vulnerability. Additional views were collected on research tools. Consensus-by-design was explicitly avoided. Data collection and processing was independent.

Results
Both panels showed surprising convergence on the pathways of vulnerability to health/illhealth, and their interaction. The agreed conceptual model describes a dynamic relation between health and ill-health and vulnerability. The 2 key pathways that link to vulnerability, are complementary, but not symmetrical as biological processes of maintaining health or obtaining better health are not reciprocal to recovery, so also not in terms of vulnerability impacts. An individual’s degree of vulnerability is the net balance of risk effects and protective and healing factors (socially, biologically and in terms of health literacy and health care access). These factors can for measurement purposes (according to the panels: interview for exploration, checklists for population research) be grouped into ‘material resources’, ‘taking responsibility for one’s own health’, ‘risky activities and behaviors’, and ‘social support’. Supportive and transforming action can thus be undertaken.

Conclusion
A universal concept of vulnerability in the context of health was successfully derived after careful replication and extension of an international Delphi study on vulnerability among the elderly

Additional Metadata
Persistent URL dx.doi.org/10.1371/journal.pone.0212633, hdl.handle.net/1765/115133
Citation
de Groot, N, Bonsel, G.J, Birnie, E, & Valentine, N.B. (2019). Towards a universal concept of vulnerability: Broadening the evidence from the elderly to perinatal health using a Delphi approach. doi:10.1371/journal.pone.0212633