Within the context of health and health systems, pursuing equity requires the identification and addressing of those determinants that systematically restrict or prevent access to particular groups. Pursing equity also requires the institution of processes that enable population groups to help to identify the systems that perpetuate inequities as well as possible solutions to reduce or eliminate disparities.

As such, vulnerability is often contextual, dependent on social and cultural systems and political and economic trends. Groups experience social vulnerability based on shared racial, ethnic, cultural, and situational similarities. The paper by Ravindran in this series for instance, provides a critical analysis of the importance of gender in defining and assessing effects of vulnerability and of equity in achieving universal coverage. The capacity to cope with risks that endanger health is further compromised by poor access of the group to resources and information; social support and social networks; political participation and representation; and access to social safety nets [6,7]. Social vulnerability is also created by discrimination, isolation, and human rights violations [8]. The homeless, elderly, refugees and migrants, sex workers, people with mental illnesses, disabilities and chronic illnesses, sexual minorities, and the medically uninsured are some groups that experience social vulnerability because of the common resource and capacity deficits brought about by their shared racial, ethnic, cultural and geographical similarity. Social vulnerability may also play out through shared physical spaces such as neighbourhoods with high violence and crime rates or conflict affected areas. Groups that are vulnerable because of deficits in their collective access to resources also tend to experience poorer health outcomes [8-10].

As entities, health systems may also be vulnerable – at a macro level vulnerability occurs when they are marginalised within political and national priorities; and at a macro level where the pillars that make up the health system are fragile. Robust health systems moderate the effects of health risks and vulnerabilities [15] by providing a continuum of health services including primary, secondary and tertiary prevention, as well as other intersectoral actions to protect and promote health. Care is not guaranteed simply by the existence of medical facilities [12] (p 9), the facilities in turn need to be strong and equitable to cope with potential access by all.

Vulnerability of health systems translates into reduced protective resources and poor health outcomes for individuals and groups, and forfeiture of potential national socio-economic gains. In addition, the population level and global dimensions of health problems witnessed in relation to HIV and AIDS, severe acute respiratory syndrome (SARS), and recent disasters as in Haiti and Fukushima are also a reminder of the significance of the resilience and vulnerability of health systems in relation to population and global health.

Similarly, an assessment of the vulnerabilities of health systems provides a useful tool to assess the ability of the health system to withstand the pressures of various population groups. The vulnerability of health systems underscores the importance of good governance, balanced and equitable development, and peace in achieving positive health outcomes and building robust health systems. Risks to the resilience and integrity of people and health systems reflect structural inequalities and inequities which need to be addressed strategically and with urgency.