There does however remain a significant subset of vulnerable patients, primarily those with CLL, B-cell lymphomas, myelofibrosis, and those on specific therapies (B-cell depleting monoclonal antibodies, BTK-, BCL2- and JAK-STAT-inhibitors) who continue to have suboptimal vaccine responses even after three doses and likely remain vulnerable to severe infection, and who may benefit most from pre-emptive or prophylactic nMAB therapies. Here, BTK is linked to infection.