Abstract: With the rapid onset of the COVID-19 pandemic, we recognize there is a significant gap in knowledge in the field on the contribution of immune functions involved in preventing infection, in modifying COVID-19 disease, and in clearing viral infection. We believe the HVTN is well placed to study these gaps and rapidly deploy this information in the development of SARS-CoV-2 neutralizing vaccines and mAb therapies. In this study we propose initiating an observational cohort study of approximately 400 persons in the United States (22 trials sites) and Peru (5 sites) convalescing from SARS-CoV-2 infection. Participants will be recruited from a variety of risk groups and clinical cohorts: hospitalized vs. non-hospitalized, symptomatic vs. asymptomatic, adults between 18 and 55 years of age and those older than 55 years, and persons with high interest clinical or virologic presentations (e.g., persons who developed myocarditis/pericarditis, required intubation, had prolonged viral shedding, or who develop a positive virologic test after initially clearing the infection). Specific aims of this study include identifying serologic reactivities that differentiate SARS-CoV-2 infection from vaccination, to develop and qualify a suite of immunologic assays and reference reagents that will permit detailed interrogations of the immune response to infection, to measure SARS-CoV-2 adaptive response in key populations and risk groups, and to characterize presentations of the infection among convalescent individuals. This initial study will tell us much about the adaptive immune responses in persons who have been infected and recovered from SARS-CoV-2 and will shed light on the role the immune system plays in successfully clearance of infection. It will improve our understanding of the dynamics and duration of responses, as well as the epitope specificity and other defining signatures, and will inform rational design and testing of preventive and therapeutic vaccines and monoclonal antibodies. In addition, this protocol will lay the groundwork for prospective studies of this infection, better defining key risk groups and knowledge gaps. Lastly, this study will prepare the network for the large number of COVID-19 vaccines now entering the clinical trial pipeline. Laboratory, statistical and operational experience in this first trial will be invaluable preparation and priming of network machinery as the HVTN prepare to roll-out several efficacy trials as part of the joint NIAID COVID Prevention Network in coming months.