Title: Effectiveness of Concurrent Care to Improve Pediatric and Family Outcomes at End of Life This grant proposal represents a first competitive renewal (Cycle 2) of a highly productive, NINR-funded research program investigating a health policy intervention for children and adolescents with serious illness. The Cycle 1 research question was whether pediatric concurrent care (simultaneous hospice and medical care) affected pediatric and family outcomes. A significant increase in fragmented care transitions and a high risk of adverse outcomes was identified, along with a cohort of rural children and adolescents significantly affected by this care environment. In response, Medicaid programs in several states ushered in transitional care regulations (TCR) for pediatric concurrent care that mandated collaborative team efforts from nurses, physicians, pharmacists, child life specialists, and other health care professionals to support and coordinate pediatric end-of-life care across settings during concurrent care. In Cycle 2, the proposed policy effectiveness project focuses on advancing pediatric health policy and health equity by examining this policy modification within a rural cohort. The project’s specific aims are to: (1) estimate the effect of the TCR intervention on rural children’s end-of-life health (i.e., functioning) and health care (i.e., resource use, spending); (2) identify a subgroup of disadvantaged rural children using innovative machine learning methods; (3) examine potential mechanisms and pathways that may inform further policy improvement strategies important to rural children and families. These aims will be achieved by conducting a multi-level natural experiment with a difference-in- difference analysis, supervised and unsupervised machine learning, and mediation and moderation analysis. The project team has the expertise in pediatric concurrent care, data science and statistical analysis. Practice partner includes the National Network of Pediatric Palliative Care Coalitions. The project is innovative because it advances the understudies area of policy-focused effectiveness science. The project is significant and will have an impact because it focuses on a major policy modification and because it will generate knowledge to inform rural health care for children. The project is aligned with NINR’s Strategic Plan, which prioritizes social determinants of health such as rurality, health equity for underserved rural children, and systems and models of care.