Similar results have been described in patients with Waldenstrom’s macroglobulinemia under therapy with rituximab or BTK-inhibitors [44], as well as in patients with multiple myeloma under treatment with anti-CD38 or anti-BCMA-based regimens [45], suggesting that therapies targeting lymphocytes and plasma cells lead to poor antibody responses after vaccination against SARS-CoV-2. Here, BTK is linked to Waldenstrom macroglobulinemia.