Severe COVID pneumonia and undetectable B cells after vaccination in patients previously treated with rituximab: a case series.

INTRODUCTION: The risk of developing severe COVID-19 illness despite completing vaccination for patients who have previously received immunosuppressive therapy is unclear. CASE PRESENTATION: We present three patients who received rituximab for treatment of autoimmune disorders who subsequently developed severe COVID-19 pneumonia post-vaccination requiring intensive care unit admission and found to have undetectable B cells. DISCUSSION: While there have been concerns about the effectiveness of COVID-19 vaccines in this patient cohort, this is the first case series to report development of severe COVID-19 illness after completing vaccination in those who previously received rituximab. Guidelines for the optimal timing of COVID-19 vaccination in relation to immunosuppressive therapy have been recently published, albeit after many patients in this subpopulation have already been vaccinated. CONCLUSION: This case series brings attention to the limited humoral response to vaccines in patients treated with rituximab, highlights existing guidelines and their limitations, and raises future considerations about the potential benefits to testing vaccine responsiveness.