Honoring Our Promises through Expedition for Afghan SIVs Act of 2021 or the HOPE for Afghan SIVs Act of 2021 This bill authorizes the Department of State or the Department of Homeland Security (DHS) to postpone the medical exam requirement for qualifying citizens or nationals of Afghanistan seeking entry into the United States as special immigrants. Specifically, this bill applies to an existing program that provides special immigrant status to an individual (or the spouse or child of such an individual) who (1) faithfully performed sensitive and trusted duties for the U.S. government or the International Security Assistance Force in Afghanistan on or after October 7, 2001, and (2) has experienced or is experiencing an ongoing serious threat due to the performance of those duties. Under this bill, the State Department or DHS may waive any requirement for such an individual to undergo a medical exam before admission into the United States. If an individual receives such a waiver, DHS shall ensure that individual undergoes a medical exam no later than 90 days after admission into the United States.