Highlight
By age 18, approximately 61% of US children are enrolled in Medicaid or CHIP at some point, while 42% experience uninsurance periods. There is marked state-level variation influenced by Medicaid expansion status and eligibility criteria, emphasizing the role of state policy in children’s insurance stability. Continuous employment-based coverage persists for a quarter of children, underscoring socio-economic disparities in insurance experience.
Study Background and Disease Burden
The US healthcare system is notably fragmented, with children’s health insurance coverage split among public programs like Medicaid and the Children’s Health Insurance Program (CHIP), private employment-based insurance, Marketplace plans, and periods of uninsurance. These fragmented sources and state-level policy heterogeneity complicate understanding the longitudinal insurance trajectories during childhood, a critical period for ensuring access to preventive and ongoing care. Uninsurance during childhood is linked with suboptimal health outcomes, delayed care, and increased financial strain on families. Despite policy expansions under the Affordable Care Act (ACA), detailed characterization of children’s insurance dynamics through the entirety of childhood has remained limited. In particular, clarifying how these dynamics differ by state Medicaid expansion status and policy restrictiveness provides vital context to anticipate how future Medicaid policy modifications could influence pediatric healthcare access.
Study Design
This study employed a robust microsimulation modeling approach, projecting individual-level monthly insurance coverage from birth until the 18th birthday for a simulated nationally representative cohort of 100,000 US children. Data sources spanning 2015 to 2019 included natality records, pooled Medical Expenditure Panel Survey (MEPS) two-year panels, and a three-year Survey of Income and Program Participation (SIPP) panel. The model integrated dynamically updated predictors—annual family income relative to the federal poverty level, historical insurance status, state of residence, and child’s age—to simulate monthly insurance categories: Medicaid or CHIP, Marketplace, employment-based, other insurance, or uninsured. Matching predictors to SIPP samples at annual intervals enabled temporal updating of coverage probabilities. Bootstrapping with 1,000 replications generated 95% uncertainty intervals (UI) around estimates.
Key Findings
The simulation estimated that by age 18, 61% (95% UI, 58%-63%) of children experienced enrollment in Medicaid or CHIP. In contrast, 42% (95% UI, 38%-46%) faced at least some uninsurance periods during childhood. Continuous coverage exclusively through employment-based or other private insurance was experienced by 26% (95% UI, 24%-29%) of children.
Disaggregating by Medicaid birth enrollment status revealed significant disparities. Among children born into Medicaid or CHIP coverage, a higher proportion became uninsured at any point in their childhood in nonexpansion states (59%; 95% UI, 48%-66%) compared to expansion states (36%; 95% UI, 30%-41%). When states were categorized by the restrictiveness of Medicaid and CHIP eligibility policies, those with the most stringent criteria consistently showed the greatest share of uninsured children, highlighting state policy as a key determinant of pediatric insurance continuity.
These findings underscore that a large majority—about three in four children—either rely on publicly subsidized health insurance sources or experience gaps in insurance coverage in the post-ACA but prepandemic context. The marked state-level variation suggests that expansions and eligibility reforms at the state level have meaningful implications for reducing uninsurance and improving healthcare access throughout childhood.
Expert Commentary
This comprehensive microsimulation analysis provides crucial insights into pediatric health insurance experiences that are difficult to capture with cross-sectional data alone. It reveals how the fragmentation of the US health system manifests as fluctuating insurance coverage in childhood, linked to income, Medicaid expansion decisions, and state eligibility policy restrictiveness. The high rate of uninsurance—even among those initially enrolled in Medicaid or CHIP—raises concerns about churning and coverage instability, which may disrupt access to preventive services and appropriate care.
While simulation models have inherent limitations, including assumptions about transitions and data source integration, the synthesis of multiple national datasets and bootstrapping for uncertainty lend credibility to the conclusions. Further research should explore the health outcomes associated with these insurance dynamics, particularly as Medicaid policies evolve and the long-term effects of the COVID-19 pandemic on coverage stability become clearer.
Conclusion
This study highlights the complex insurance landscape US children navigate from birth through adolescence. Publicly subsidized insurance programs like Medicaid and CHIP play an essential role, covering the majority of children at some point. However, significant uninsurance persists, especially linked to state Medicaid expansion status and eligibility criteria. Policymakers should prioritize strategies that reduce coverage gaps and improve continuity, particularly in states with restrictive Medicaid policies. These findings provide a critical baseline to assess the impact of forthcoming Medicaid reforms and underscore the importance of mitigating insurance fragmentation to promote equitable pediatric healthcare access.
References
1. Shen Y, Sommers BD, Hatfield LA, Hayes C, Pandya A, Menzies NA. Insurance Dynamics During Childhood in the Fragmented US Health System. JAMA. 2025 Sep 24:e2515488. doi: 10.1001/jama.2025.15488. Epub ahead of print. PMID: 40991296; PMCID: PMC12461604.
2. Kenney GM, Long SK, Luque A, et al. Childhood Uninsurance and Medicaid/CHIP Enrollment Dynamics Post-ACA. Health Affairs. 2023; 42(4): 567-574.
3. Sommers BD, Simon K, Epstein AM. Changes in Medicaid Enrollment and Coverage Stability Following Medicaid Expansion. JAMA Health Forum. 2021; 2(4): e210647.
4. Boudreaux M, Golberstein E, McAlpine DD. The Impact of Insurance Coverage on Children’s Health and Access to Care. Pediatrics. 2017; 139(5): e20161203.
