Predictors of low spike antibody response in patients with systemic rheumatic disease after an initial course of COVID-19 vaccination.

• More than one-third of patients with systemic rheumatic disease that had spike Ab tested in routine care had low spike Ab after 2 doses of mRNA or 1 dose of adenovirus vector COVID-19 vaccine. • Diagnosis of SLE, use of prednisone, and use of rituximab were significantly associated with greater odds of low spike antibodies. • These data underscore the importance of additional doses of COVID-19 vaccine and prophylactic Evusheld in immunosuppressed patients with systemic rheumatic disease as recommended by the US Centers for Disease Control.