CC Summary Abstract The proposed Study on Interactions between SARS-CoV-2 infection and Ancestral genomic Variations in the Risk of Alzheimer's Disease (ISAVRAD) requires significant coordination across the five data collection sites (Argentina, Nigeria, and 3 sites in the US: Texas, NY, and Washington state) and 3 research projects. In support of the goals of ISAVRAD, the Clinical Core (CC) will enroll and conduct in-depth clinical evaluations of 4,300 older adults with (75% of the sample) and without (25% of the sample) exposure to SARS-CoV-2 at baseline, and will conduct follow-up evaluations at 18 and 36 months. Clinical evaluations will include medical and epidemiological histories focused on SARS- CoV-2 infection, including COVID-19 case report forms (CRFs) harmonized by the WHO, neuropsychological assessment (including Uniform Data Set and a tablet-based, language-independent assessment), neurological examination, and completion of the semi-structured interview Schedules for Clinical Assessment in Neuropsychiatry of the World Health Organization (WHO SCAN), as well as informant report. At all data collection time-points, the CC will also collect and ship blood biospecimens to carry out point-of-care COVID-19 antibody testing, extract DNA, and bank whole blood and plasma for future collaborative studies. It will also screen participants for MRI and harmonize MRI and PET data acquisition at all sites, sending imaging results to the Neuroimaging Core. The CC will also conduct case conferences to assign diagnostic clinical outcomes according to cognitive impairment level/ADRD status (unimpaired, Mild cognitive impairment, dementia syndrome with disease-specific etiologies). Disease specific etiologies will include AD, Lewy-Body Dementia, Vascular Dementia, Frontal Lobe Dementia, and mixed. Finally, the CC will employ a sophisticated data capture system, collaboratively developed with the Data Management and Statistics Core, to provide real- time data transmission to the ISAVRAD database via RedCAP. The CC will be co-lead by Dr. Gabriel A. de Erausquin Thomas Patterson, Dr. Sudha Seshadri, and Mindy Katz, MPH with the assistance of site PIs Rufus Akinyemi (Nigeria), Agustin Yecora (Argentina) and Malveeka Sharma (Seattle). In addition to already having a strong working relationship, they have decades of experience in data collection from diverse and understudied cohorts, longitudinal data collection, and recruitment of persons with dementia.