Vaccination for SARS-CoV-2 in Hematological Patients

Patients with specific hematological malignancies (HM) are at increased risk for severe disease and death from infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In healthy subjects, vaccination against SARS-CoV-2 has been demonstrated to be highly effective in disease prevention; however, immunocompromised patients were largely excluded from vaccine randomized controlled trials. In this review, we overview available non-randomized studies addressing effectiveness and safety of several coronavirus disease 2019 (COVID-19) vaccines in patients with HM. Overall, COVID-19 vaccines are safe in patients with HM, with adverse events similar to those in the general population. Though serology testing is not recommended as a test to evaluate vaccine effectiveness, a correlation between higher antibody levels and protection against infection has been reported. Studies evaluating humoral response to COVID-19 vaccine in HM patients demonstrate low immunogenicity, mainly in patients with lymphoproliferative disorders, as well as with certain drugs, including mainly anti-CD20 antibodies, Bruton tyrosine kinase inhibitors, and also ruxolitinib and venetoclax. Seropositivity rates of patients with non-Hodgkin lymphoma and chronic lymphocytic leukemia following mRNA vaccination reach 40%-50%. T-cell responses to vaccination are also impaired among these patients. Better humoral response rates are reported in multiple myeloma patients and hematopoietic stem-cell transplant, reaching ∼75%-80%, but not in patients following chimeric antigen receptor T-cell therapy. Patients with chronic myeloid leukemia and myeloproliferative diseases have high response rate to vaccination. Third mRNA vaccine dose is currently recommended to all HM patients. Alternative approaches for vaccination and prevention in patients unable to mount an immune response following full vaccination are provided in the review.