COVID-19 vaccination substantially reduces morbidity and mortality associated with SARSCoV-2 infection and severe illness. However, despite the availability of effective COVID-19 vaccines, many questions remain about the efficacy of these vaccines and the durability and robustness of immune responses, especially in immunocompromised persons. We propose a single two-year data pooling project that merges data from both (i) electronic medical records, as well as (ii) prospective vaccine response study cohorts from 11 Serological Sciences Network (SeroNet) sites across the U.S. The coordinated effort of multiple SeroNet sites is crucial for generating results more generalizable to the wider U.S. population, including investigation of sources of vaccine response heterogeneity (e.g., age, sex, race/ethnicity and geography).