Project 1 Summary We will conduct comprehensive studies of immune responses in human subjects who have current or past infections with SARS-CoV-2. An overarching aim is to understand whether immune responses to CoV-2 infections confer protection against future repeat episodes of COVID19 and whether CoV-2 immunity is long lasting. We propose the hypothesis that once immunocompetent human beings have had any form of COVID19, they will never get the full disease again. On the other hand, long term follow-up studies of CoV-2 immunity in patients with cancer or any cause of immunodeficiency will include plans to look for reinfection and repeat episodes of COVID19. There is a clear need for accurate serologic assays to determine who in a given community has had infection with SARS CoV-2. Many assays marketed early in the pandemic are prone to false positive and negative results. We plan to validate our efficient and sensitive immunoassays for routine serodiagnosis of SARS CoV-2 infections. It should be admitted that even the best assay is going miss unusual cases where a person tested positive by PCR but shows up negative in antibody tests. Although the antibody assay could be falsely negative, it is also possible that the person was truly infected by did not develop humoral immunity. In project 2, we will test the possibility that measuring T cell immunity may confirm that even some antibody negative patients have immunity to the virus after all.