this part. (iii) Limitation on secretarial claims through subrogation The Secretary shall not assert any claim on behalf or against a prescription drug plan, other than through the recovery from such a plan of amounts paid related to a covered part D drug event that has been repaid to the plan through a subrogation action or otherwise. (iv) Primary drug plan defined In this paragraph, the term primary drug plan means, with respect to benefits for covered part D drugs, a group health plan or large group health plan (other than a group health plan or multiemployer or multiple employer plan of, or contributed to by, an employer that has 20 or fewer employees for each working day in each of 20 or more calendar weeks in the calendar year involved or the preceding calendar year), a workers’ compensation law or plan, an automobile or liability insurance policy or plan (including a self-insured plan) or no-fault insurance insofar as such a plan, law, policy, or insurance provides such benefits, insofar as, under the provisions of section 1862(b)(2), such coverage would be treated as a primary plan if benefits for covered part D drugs were treated as benefits under parts A and B. For purposes of this clause, an entity that engages in a business, trade, or profession shall be deemed to have a self-insured plan if it carries its own risk (whether by a failure to obtain insurance, or otherwise) in whole or in part. (B) Waiver A prescription drug plan may waive (in whole or in part) the provisions of this paragraph in the case of an individual claim if the plan determines that the waiver is in the best interests of the program established under this part. (C) Recovery A prescription drug plan shall be subrogated (to the extent of payment made under this part by the plan for any covered part D drug before the date the plan received notice pursuant to subparagraph (D)) to any right of an individual or any other entity to payment, with respect to such covered part D drug, under a primary drug plan. A subrogation claim may not