Patients who have undergone hematopoietic cell transplantation (HCT) or have received chimeric antigen receptor T-cell (CAR-T) therapy often have poor outcomes after developing COVID-19, and do not respond to vaccination. In this video, Muhammad Bilal Abid, MD, MRCP, Medical College of Wisconsin, Milwaukee, WI, discusses a study which aimed to investigate whether administering a third dose of the COVID-19 mRNA vaccine to these patients could counteract waning immunity. Dr Abid gives a detailed explanation of the patient inclusion and exclusion criteria, and concludes by describing the assay used to detect antibody levels in patients at different time points throughout the study. This interview was recorded via an online conference call with The Video Journal of Hematological Oncology (VJHemOnc).