Study inclusion flowchart. ^aPersons deemed eligible during screening process, but staff unable to approach or consent (eg, too ill to approach, transferred to outside facility before approached, mental status did not permit consent). ^bPersons deemed eligible during screening process, but upon approach determined ineligible (eg, not AI/AN, non-ARI illness). ^cExclusion categories were not mutually exclusive, and individual categories may not sum to total excluded. Abbreviations: AI/AN, American Indian and Alaska Native; ARI, acute respiratory illness; IRB, institutional review board; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TN, test-negative; VE, vaccine effectiveness.