MediKids Health Insurance Act of 2003

MediKids Health Insurance Act of 2003 - Amends the Social Security Act (SSA) to allow certain eligible individuals born after December 31, 2004, who have not attained age 23, to enroll in the MediKids Program under new SSA title XXII established by this Act for entitlement to benefits specified by the Secretary of Health and Human Services (HHS). Includes among such benefits early and periodic screening, diagnostic services, and treatment services under Medicaid (SSA title XIX), and prescription drugs and biologicals. Provides for: (1) cost-sharing; (2) a payment schedule for covered benefits; (3) a monthly MediKids premium and the means for payment of it; and (4) a reduction in premium for certain low-income families.

Creates in the Treasury the MediKids Trust Fund for collected premiums, appropriated amounts, and other revenues for use in funding the coverage provided under the MediKids Program and maintaining its financial solvency.

Authorizes the Secretary to implement a care coordination services program including specified elements under which eligible individuals may elect to have health care services covered under SSA title XXII managed and coordinated by a designated care coordinator.

Amends SSA title XVIII (Medicare) to increase the membership of the Medicare Payment Advisory Commission, with the initial terms of additional members staggered.

Amends the Internal Revenue Code to: (1) impose a MediKids premium tax in the case of any taxpayer (with certain exceptions) required to pay a premium under the MediKids Program for an eligible individual; and (2) provide for a refundable tax credit for 50 percent of cost-sharing expenses under the MediKids Program.

Directs the Secretary of the Treasury to propose a gradual schedule of progressive tax changes to fund the MediKids Program as the number of enrollees grows in the out-years.