From the Purpose: "U.S. Citizenship and Immigration Services (USCIS) is updating guidance in the USCIS Policy Manual [hyperlink] regarding health-related grounds of inadmissibility in accordance with recently updated requirements issued by the Centers for Disease Control and Prevention (CDC). The updated guidance, which is effective October 1, 2021, requires applicants subject to the immigration medical examination to submit COVID-19 [coronavirus disease 2019] vaccination records before completion of immigration medical examinations conducted in the United States and overseas."
PA-2021-20; Policy Alert-2021-20
U.S. Citizenship and Immigration Services: https://www.uscis.gov/