Health system-community partnerships in a Medicaid nutrition and housing program, 2020-2023: a mixed-methods evaluation.

INTRODUCTION: Health systems are partnering with social service organizations (SSOs) to establish health-related social needs (HRSN) programs, yet best practices have not been established. METHODS: This study assessed the implementation of a partnership between one accountable care organization (ACO) and SSOs in Massachusetts' Medicaid Flexible Services Program (FSP) from 2020 to 2023 to address food and housing insecurity. To be FSP-eligible, individuals needed to be in the ACO, have food or housing insecurity, and meet specific health criteria. Quantitative measures of reach, enrollment, and services were integrated with findings from interviews with ACO (n = 12) and SSO (n = 11) staff. RESULTS: Overall, 15.1% of 16 289 FSP-eligible adults and 11.8% of 5476 FSP-eligible children were enrolled. Nutrition enrollments increased over time, but housing enrollments remained low. ACO and SSO staff described positive impacts, including tailored support for patients' needs, SSO organizational growth, and understanding of how SSOs can partner with health care. Implementation challenges included complex contracts, administrative burden, and housing shortages. State funding for SSO infrastructure, cross-sector data sharing, workflow simplification, and ACO-SSO communication improved efficiency and reduced burden. CONCLUSION: The ACO-SSO partnerships expanded resources to address beneficiaries' HRSN. Understanding factors that contribute to success on both sides of the partnership can inform future HRSN programs.