To support the research goals of our CCHI, the Clinical and Biostatistical Core proposes to continue long-term follow up of our established COVID-19 cohort of 747 patients over the next 5-year grant cycle. The unique features of COVID-19 immunity can be explored in this cohort, which presents an incredible opportunity to advance mechanistic insight into the induction of innate and adaptive immunity to a novel, highly transmissible pathogen that poses ongoing threats to human health. Knowledge gained from these immunological studies can inform approaches to control future emerging human coronaviruses that could become major public health concerns. The Specific Aims of the Clinical Core are: Aim 1. Provide the clinical infrastructure and expertise for conducting human research to improve mechanistic understanding of immunity following vaccination and infection among different age groups. Aim 2. Define immune memory in study participants enrolled in our COVID-19 longitudinal cohort who recover or experience Long COVID. Aim 3. Provide statistical, modeling, and data management expertise that ensures the success of the CCHI scientific agenda