Defense of Medicare Act

Defense of Medicare Act - Directs the Secretary of Health and Human Services, in applying risk adjustment factors to payments to Medicare+Choice organizations under part C (Medicare+Choice) of title XVIII (Medicare) of the Social Security Act (SSA), to ensure that payments to such organizations are adjusted based on factors that ensure that the health status of the enrollee is reflected in such adjusted payments, including adjusting for the difference between the health status of the enrollee and individuals enrolled under the original Medicare fee-for-service program under Medicare parts A (Hospital Insurance) and part B (Supplementary Medical Insurance). Requires payments to such organizations, in the aggregate, to reflect such differences.

Amends SSA title XVIII part C, as amended by the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, to: (1) revise the formula for determination of the minimum annual Medicare+Choice (Medicare Advantage) capitation rate for 2005 and subsequent years (making it the same as the minimum rate for 2004); and (2) eliminate the Medicare Advantage (MA) Regional Plan Stabilization Fund.

Repeals the Comparative Cost Adjustment Program.

Amends SSA title XVIII, as amended by the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, to require the Secretary to ensure that each individual eligible for such program has available a choice of enrollment in at least two prescription drug plans (currently, at least two qualifying plans, which may be a prescription drug plan or a specified Medicare Advantage-Prescription Drug (MA-PD) plan).