Medicaid and the Children’s Health Insurance Program (CHIP) play critical roles in US child health coverage, but children frequently endure uninsured periods, and recent federal health policy changes may worsen existing gaps, found a new microsimulation modeling study published in JAMA.

Ye Shen, MSPH, a researcher in the Interfaculty Initiative in Health Policy at Harvard University in Cambridge, Massachusetts, and colleagues estimated insurance dynamics from 2015 to 2019 in relation to Medicaid or CHIP and lack of insurance in childhood under the Affordable Care Act (ACA)’s prepandemic policy conditions.

“Studying longer-term insurance transitions in the United States has been difficult because existing insurance data sources are either fragmented or too limited in follow-up time. As a result, the extent of children’s cumulative insurance experiences over the first 18 years of life has remained unclear,” Shen told Medscape Medical News. “Our study sought to fill this gap by combining multiple national socioeconomic, demographic, and insurance data sources to develop a microsimulation model.” 

The model projected individual-level monthly insurance coverage for 2015-2019 across five types: Medicaid or CHIP, ACA Health Insurance, employment-based, other, or uninsured from birth until the 18th birthday for a simulated nationally representative cohort of 100,000 US children.

Modeling data were drawn from several sources, including the Survey of Income and Program Participation, 2017-2019; CDC WONDER natality records, 2016-2019; state Medicaid and CHIP policy information for 2019; and sex-specific life tables for 2019. Predictors included annual family income as a percentage of the federal poverty level, insurance history, state, and age.

An estimated three of four US children relied on publicly subsidized insurance or experienced a period without any insurance by their 18th birthday in that prepandemic environment. Substantial state heterogeneity in insurance coverage supports the critical role of Medicaid policies, the authors stressed. More than six out of 10 children rely on Medicaid or CHIP, rising to more than three quarters of Black and Hispanic youngsters.

Specifically, by their 18th birthday, 61% (95% uncertainty interval [UI], 58%-63%) of US children were ever enrolled in Medicaid or CHIP and 42% (95% UI, 38%-46%) were ever uninsured. The authors estimated that 42.3% of US children will experience a period with no insurance by age 18, and an additional 17.9% will experience disruptive transitions between insurance coverage during childhood.

An estimated 26% (95% UI, 24%-29%) were continuously enrolled in employment-based or other insurance excluding Medicaid, CHIP, or ACA Marketplace. The proportion of children born with Medicaid or CHIP coverage who were ever uninsured was 59% (95% UI, 48%-66%) in ACA nonexpansion states vs 36% (95% UI, 30%-41%) in expansion states.

The situation is only expected to worsen with the Budget Reconciliation Act of 2025, which proposes to cut $990 billion in federal Medicaid spending over the next 10 years and remove millions of people from Medicaid.

“Our main findings show that Medicaid and CHIP touch the lives of most American children, suggesting that substantial policy changes may have widespread impact,” Shen said. “In addition, childhood coverage gaps were already substantial even before these changes and now risk becoming worse.”

She noted that in July the Center for Medicare & Medicaid Services stopped approving waivers for multiyear continuous eligibility for children. That same month, the federal Budget Reconciliation Bill was signed into law, with the Congressional Budget Office projecting a trillion dollars in reduced Medicaid spending and 10-15 million fewer enrollees by 2034.

Medicaid coverage losses in expansion states could spill over to disrupt children’s coverage, said Shen. “In a fragmented insurance landscape, children need policies that help them get covered, and just as importantly, stay covered.”

Offering her perspective on the study, Sarah Gordon, PhD, MS, an assistant professor of health law, policy, and management at Boston University School of Public Health in Boston, called it “important for establishing a baseline to gauge upcoming policy changes that will reduce Medicaid funding and negatively impact continuity of coverage for parents, with potential spillover effects on children.”

“The finding that 42% of children were ever uninsured is much higher than previously reported rates and illustrates the gaps in our patchwork of health insurance systems, even for the nation’s children,” Gordon told Medscape Medical News.

She added that efforts at the state level are needed to minimize administrative burdens that lead to unnecessary gaps in coverage for children and families and to protect network capacity of child healthcare providers and specialists who accept Medicaid amid ongoing funding cuts.

And in an accompanying editorial, Aditi Vasan, MD, MSPH, a pediatrician at Children’s Hospital of Philadelphia in Philadelphia, and a colleague said the study underscores the importance of examining longitudinal trajectories of coverage. “Although recent estimates suggest about 6% of children in the US are currently uninsured, Shen et al show that transient periods of uninsurance during childhood are far more common.”

The editorial commentators added that healthcare providers, researchers, and policymakers should consider how to protect children from immediate adverse impacts. “As clinicians, we must recognize when our patients and their caregivers are faced with coverage loss or unexpected transitions between insurance programs and collaborate with local legal aid and advocacy organizations to help smooth these transitions and minimize gaps in care.”

Furthermore, researchers should rigorously examine the effects of policy changes on children’s health coverage, care access, and health outcomes to inform future policies, while policymakers should consider the country’s obligation to provide continuous coverage and care to its youngest and most vulnerable residents.

This study had no specific funding. Shen had no competing interests. Coauthor Sommers reported receiving grants from the Commonwealth Fund, Episcopal Health Foundation, and United Hospital Fund, as well as honoraria from Kinetix Group, Massachusetts Psychiatric Society, and the American Medical Association and travel support from Academy Health outside of the submitted work. Gordon had no conflicts of interest relevant to her comments. Vasan reported receiving grants from the Agency for Healthcare Research and Quality outside of the submitted work. Editorial coauthor Eliason reported receiving grants from the National Institute of Child Health and Human Development outside of the submitted work.