Final answer:
The most recent addition to the Medicare program is the Prescription Drug Benefit, implemented as part of the Medicare Prescription Drug and Modernization Act of 2003 to help cover medication costs for the elderly and disabled.
Step-by-step explanation:
The latest addition to the Medicare program is the Prescription Drug Benefit, which was a part of the Medicare Prescription Drug and Modernization Act of 2003. This expansion helped the elderly and disabled who needed assistance with the costs of their prescription medications. The introduction of this benefit was a significant change to Medicare, responding to the program's previous gaps in coverage and providing much-needed support for those with high medication costs.