States are no longer required to report to the Centers for Medicare & Medicaid Services (CMS) vaccination data for children in the Medicaid and CHIP programs. These programs cover nearly half of all American children. The new CMS policy means there will be less information about the health of these children. The change concerns the reporting of vaccination rates. Medicaid and CHIP are central to children's health care in the US. According to the article, this policy further undermines population immunization.