Ensuring Seniors Access to Local Pharmacies Act of 2021 This bill establishes several requirements for prescription drug plans under the Medicare prescription drug benefit. Specifically, the bill requires prescription drug plans to allow any pharmacy located in a health professional shortage area, a medically underserved area, or a rural area to be included as an in-network pharmacy if the plan already has other in-network pharmacies in the same area. The bill also establishes certain standards for prescription drug plans regarding pharmacy reimbursements and related disclosures. Among other things, the bill prohibits prescription drug plans from reimbursing a pharmacy in an amount that is less than the amount the pharmacy benefits manager (PBM) reimburses an affiliated pharmacy (i.e., a pharmacy that has a shared ownership interest with the PBM) for the same services.