Authorized by the Medicare Prescription Drug, Improvement and Modernization Act (MMA) in 2003 and implemented in January 2006, the Part D program covers beneficiaries through (1) a Prescription Drug Plan (PDP) for drug coverage only, or (2) a Medicare Advantage plan (MA) that covers medical services and prescription drugs (MA-PD). Medicare beneficiaries have to affirmatively choose and enroll in a plan, unless they are dual eligible, having both Medicare and Medicaid.