Our goal is to inform public health guidelines on COVID-19 vaccine and boosters to reduce SARS-CoV-2 infection and severe illness in immunocompromised populations. To do so requires large datasets of well-defined populations with clinical information and a robust collaborative infrastructure able to evolve as new research questions arise during the pandemic. Therefore, we propose to mimic the NA-ACCORD strategy of pooling cohorts at multiple sites in North America. In this Pooling Project, we will merge data from both (i) electronic medical record (EMRs) as well as (ii) prospective cohorts from 11 geographically disperse SeroNet sites across the U.S. Data harmonization efforts will be streamlined, and analyses will be divided by research area across all sites to allow multiple publications to occur simultaneously.