CHIP shots: association between the State Children's Health Insurance Programs and immunization rates

The Balanced Budget Act of 1997 established the State Children's Health Insurance Program (SCHIP), which makes health insurance available to children in near-poor families who are ineligible for Medicaid. SCHIP mandates that all state plans cover the cost and administration of childhood vaccines. Whether SCHIP has narrowed immunization coverage rates between near-poor and nonpoor children is unknown. The objective of this study was to use data from the National Immunization Survey from 1995 to 2002 to analyze changes in immunization coverage rates among poor, near-poor, and nonpoor children before and after implementation of SCHIP.

A prepost analysis was made of changes in immunization rates among poor, near-poor, and nonpoor children before and after implementation of SCHIP in all 50 states and 28 Immunization Action Plan areas from 1995 to 2002. All children in the National Immunization Survey for whom information on vaccinations was available from the respondents' shot cards and/or from the children's immunization providers (N = 264214) were studied. Up-to-date status for the 4:3:1 (4 doses of diphtheria-tetanus toxoids-pertussis vaccine/3 doses of poliovirus vaccine/1 dose of measles-mumps-rubella vaccine) and the 4:3:1:3:3 (4 doses of diphtheria-tetanus toxoids-pertussis vaccine/3 doses of poliovirus vaccine/1 dose of measles-mumps-rubella vaccine/3 doses of Haemophilus influenzae type B vaccine/3 doses of hepatitis B vaccine) series as well at the hepatitis B and varicella vaccines was measured.

The probability that a poor or near-poor child was up to date for the 4:3:1:3:3 vaccine series increased approximately 11 percentage points after implementation of SCHIP. However, we observed a similar increase for nonpoor children. The proportion of poor and near-poor children who were up to date for the varicella vaccine increased between 7 and 8 percentage points more than among nonpoor children after implementation of SCHIP. Relative increases among poor and near-poor children were greater in the 28 Immunization Action Plan areas, in states with high rates of uninsured children, and among Hispanics.

SCHIP seems not to be associated with changes in the up-to-date status of poor and near-poor children for the 4:3:1 and the 4:3:1:3:3 vaccine series. Vaccine coverage rates increased broadly among all income groups between 1995 and 2002.