rituximab therapy, a CD-20 monoclonal antibody, may have a blunted immune response to the COVID-19 vaccine.; vaccination failure; COVID-19 infection; decrease humoral immune response; This is a literature report from the Agency.  A 78 year old female with a medical history of Non Hodgkin Lymphoma receiving bimonthly treatments of rituximab since her diagnosis in 2019 presented with a worsening cough for two weeks. The patient was afebrile, without leukocytosis, and tachypneic at 25 breaths per min. Chest Xray showed bilateral infiltrates. CTA of the chest was remarkable for ground glass opacities, without evidence of thromboembolism. The patient tested positive for COVID 19 infection on arrival. The patient never had a prior COVID 19 infection. She received the COVID 19 vaccine (COVID-19 VACCINE- MANUFACTURER UNKNOWN) as directed, with her last dose 10 weeks before hospital admission. Of note, she received a dose of rituximab 9 days following her first dose of the COVID 19 vaccine and likely did not mount an adequate immune response to the COVID 19 vaccine since she was concurrently being treated with rituximab. The Author reported that a patient being treated with a chimeric CD20 monoclonal antibody like rituximab could decrease COVID 19 vaccine effectiveness. Rituximab is a CD20 monoclonal antibody used in treating B cell malignancies and autoimmune disorders. It targets the CD20 antigen on the surface of normal and malignant B cells. By inhibiting the cells functionality, humoral responses to foreign antigens could be blunted. The half life of rituximab is approximately 20.8 days. Total B Cell depletion is observed within the first 24 to72 hours after the first infusion. Complete recovery of B cells is not appreciated until 9 to12 months following treatment. Prolonged B cell depletion as described has been shown to decrease humoral immune response to neoantigens. Studies have shown patients undergoing CD 20 monoclonal antibody treatment have a blunted immune response to vaccination. Patients in states of B cell depletion after rituximab therapy have already shown a decrease in response to influenza, Hib, and PPV 23 vaccination up to 10 months after the last treatment.  Pfizer is a marketing authorization holder of rituximab and BNT162B2 in the country of incidence or the country where the product was purchased (if different). This may be a duplicate report if another marketing authorization holder of rituximab and COVID 19 vaccine has submitted the same report to the regulatory authorities.; Sender's Comments: A contributory role of the suspect drugs cannot be excluded for events humoral immune defect, vaccination failure, and COVID-19 based on temporal association and drug interaction between the two products. This case will be reassessed upon receipt of additional information. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.