Although no cases of SARS-CoV-2 transfusion-transmission have been reported worldwide, RNA is detected in 15% to 90% of patients with critical COVID-19 and 2% to 13% of individuals with mild COVID-19 symptoms. A study recently published in The Journal of Clinical Investigation adds to the growing body of evidence that the risk of transfusion-transmission is very low. From January 2020 through July 2021, four major blood collection centers (representing approximately 50% of the U.S. blood supply) investigated infectivity of 2,250 blood samples collected from individuals who self-reported post-donation COVID-19 infections and/or symptoms. Overall, 196 (8.7%) were RNA positive for SARS-CoV-2. One percent of samples were positive starting in March 2020; positivity peaked at 9% in September 2020 and 15% in March 2021, and fell to 4% in April 2021 after the introduction of widespread vaccination. The median SARS-CoV-2 viral load was estimated to be very low—6 gEq/mL— with 90% of samples having an estimated viral load of 18 gEq/mL or lower. Both cell culture and mouse models of infection found that viral loads needed to be multiple log-folds higher to be infectious via blood transfusions. These results suggest that SARS-CoV-2 is not transfusion transmissible and support the policy of not testing blood products for SARS-CoV-2.
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