California: Linking Immunization Registries to Medicaid


The California Department of Health Care Services Medi-Cal Program and the California Department of Public Health partnered to close gaps in COVID-19 vaccination data for the state population.


COVID-19-related child hospitalizations are more likely to occur in states with lower COVID-19 vaccination rates. Increasing COVID-19 vaccination rates in both children and adults can help prevent negative health outcomes in children related to COVID-19. Targeting populations with lower vaccination rates can help improve child health outcomes, but institutional barriers can impede communicating with target populations effectively. In California, Medicaid recipients had lower COVID-19 vaccination rates, including those under age 12. However, the Medicaid system did not have access to other state immunization registry data. Providers who treated Medicaid recipients did not have access to all the immunization record information to know which recipients had or had not been vaccinated against COVID-19.


California’s Medicaid providers needed access to patients’ immunization history to better prepare for and advise patients during their visits. Immunization data that does exist in the Medicaid system could be incomplete. California Medicaid partnered with the California Department of Public Health (CDPH) to link the immunization registry data to Medicaid data to track Medicaid enrollee COVID-19 vaccination status and other data points of interest. Managed care organizations (MCOs) conducted targeted outreach efforts to those not yet vaccinated.


This linking of data allowed Medi-Cal to have a better picture of COVID-19 vaccination rates among their beneficiaries. Having accurate immunization data facilitated the possibility of more efficient, targeted public health outreach.

Supplemental Resources

Years: 2023

Locations: California

Programmatic Areas: Adolescent Immunization, Adult Immunization, COVID-19, Partnerships, Public Health Functions

Key Words: Adolescents, COVID-19, Health Promotion, outbreak management, Partnership

Evidence Based: No

Evaluations: No

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