B cell depleting agents are amongst the most commonly used drugs to treat haemato-oncological and autoimmune diseases. They rapidly induce a state of peripheral B cell aplasia with the potential to interfere with nascent vaccine responses, particularly to novel antigens. We have examined the relationship between B cell reconstitution and SARS-CoV-2 vaccine responses in two cohorts of patients previously exposed to B cell depleting agents: a cohort of patients treated for haematological B cell malignancy and another treated for rheumatological disease. B cell depletion severely impairs vaccine responsiveness in the first 6 months after administration: SARS-CoV-2 antibody seroprevalence was 42.2% and 33.3% in the haemato-oncological patients and rheumatology patients respectively and 22.7% in patients vaccinated while actively receiving anti-lymphoma chemotherapy. After the first 6 months, vaccine responsiveness significantly improved during early B cell reconstitution, however, the kinetics of reconstitution was significantly faster in haemato-oncology patients. The AstraZeneca ChAdOx1 nCoV-19 vaccine and the Pfizer BioNTech 162b vaccine induced equivalent vaccine responses, however shorter intervals between vaccine doses (<1m) improved the magnitude of the antibody response in haeamto-oncology patients. In a subgroup of haemato-oncology patients, with historic exposure to B cell depleting agents (>36m previously) vaccine non-responsiveness was independent of peripheral B cell reconstitution. The findings have important implications for primary vaccination and booster vaccination strategies in individuals clinically vulnerable to SARS-CoV-2.

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