While randomized controlled trials demonstrated 94–95 % efficacy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike messenger RNA (mRNA) vaccines, efficacy in immunocompromised patients has not been established. We aimed to understand serologic response to mRNA vaccination in patients with chronic lymphocytic leukemia (CLL), a population of interest given the immunocompromised state associated with this malignancy and disease-directed therapies, as well as incomplete immune responses following other vaccinations