Thalassemia is an inherited hemoglobinopathy requiring lifelong blood transfusions and iron chelation. Chronic transfusions can lead to alloimmunization and hemolytic reactions. We discuss a patient with a well-established and stable transfusion cycle who showed signs of an acute hemolytic process following administration of the Pfizer-BioNTech COVID-19 (BNT162b2) vaccine. The patient’s pre-transfusion hemoglobin over the four weeks around vaccine administration was 1.48 g/dL lower than the pre-transfusion hemoglobin during the three months prior to and after the vaccine administration period. His bilirubin (primarily indirect) was 0.74 mg/dL higher during the vaccine period. Both values returned to baseline within two weeks following the second vaccination. This report signals a novel adverse reaction in the thalassemia population not reported in the study trials. Numerous thalassemia patients have and continue to receive this vaccine (and other vaccines) amidst this pandemic and our goal is to highlight the benefit of closer monitoring and possibly more frequent transfusions during the vaccine administration period.

Keywords: Thalassemia; Pfizer vaccine side effects; Hemolysis from COVID vaccine