LAUSR

Vaccination guidelines for patients treated for hematological diseases are typically conservative. Given their high risk for severe coronavirus infectious disease 2019 (COVID-19) it is important to identify those patients that benefit from vaccination. We prospectively quantified serum IgG antibodies to spike subunit 1 (S1)antigensduring and after 2-dose mRNA-1273 (Spikevax/Moderna) vaccination in hematology patients. Obtaining S1 IgG≥300 binding antibody units (BAU)/mlwas considered adequate as it represents the lower level of S1 IgG concentration obtained in healthy individuals andit correlates with potent virus neutralization. Selected patients (n=723) were severely immunocompromised due to their disease or treatment thereof. Nevertheless, more than 50% of patients obtained S1 IgG ≥300 BAU/ml after 2-dose mRNA-1273. All patients with sickle cell disease or chronic myeloid leukemia obtained adequate antibody concentrations.Around 70% ofpatients with chronic graftversushostdisease (GvHD), multiple myeloma, or untreated chronic lymphocytic leukemia (CLL) obtained S1 IgG≥300 BAU/ml.Ruxolitinib or hypomethylating therapy but not high-dose chemotherapy blunted responses in myeloid malignancies. Responses inlymphoma patients, CLL patients on ibrutinib, and chimeric antigen receptor T cell recipients were low.The minimal time-interval after autologous hematopoietic cell transplantation (HCT) to reach adequate concentrations was <2 months for multiple myeloma, 8 months for lymphoma, and 4-6 months after allogeneic HCT.Serum IgG4, absolute B and NK cell number and number of immunosuppressants predicted S1 IgG ≥300 BAU/ml. Hematology patients on chemotherapy, shortly after HCT, or with chronic GvHD should not be precluded from vaccination. Netherlands Trial Register NL9553.