Research is needed to provide a clearer understanding of the conditions under which particular health care systems and specific aspects of care can combine with social factors to affect social disparities in health. Social disparities in health exist for the onset of illness, as well as, for the severity and progression of disease. It is likely that primary, preventive care, along with social factors outside the healthcare system can play a key role in reducing the onset of disease. However, the provision of health insurance to socially vulnerable populations that is not accompanied by the reduction or elimination of other system barriers to care, can result in the persistence of high levels of unmet medical needs. System barriers are characteristics of the health care system that can serve as a deterrent to use such as fragmentation of services, distance, waiting time, appointment scheduling, availability of transportation and poor provider communication. Recent U.S. data document that although the proportion of kids uninsured declined as a result of the expansion of children’s health insurance between 1998 and 2006, the proportion of kids
