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Patients with beta-thalassemia show 5-fold increase in agestandardized lethality due to SARS-CoV-2 infection, representing a high-risk population compared with age- and sex-matched healthy subjects.(1) Vaccination against SARS-CoV-2 is crucial to reduce mortality and morbidity of frail patients.(2) Up to now, limited data have been available on the responses of patients with beta-thalassemia immunized with anti-SARS-CoV-2 mRNA vaccines.(3)

Background: Although numerous patient specific co-factors have been shown to be associated with worse outcomes in COVID-19, the prognostic value of thalasemic syndromes in COVID-19 patients remains poorly understood. Aims: We studied the outcomes of 137 COVID-19 patients with a history of Transfusion Dependent Thalassemia (TDT) and non-Transfusion Dependent Thalassemia (NTDT) extracted from a large international cohort and compared them with the outcomes from a matched cohort of COVID-19 patients with no history of thalasemia. Results: The mean age of thalassemia patients included in our study was 41±16 years (48.9% male). Almost 81% of these patients suffered from TDT requiring blood transfusions on a regular basis. 38.7% of patients were blood group O. Cardiac iron overload was documented in 6.8% of study patients, whereas liver iron overload was documented in 35% of study patients. 25% of thalassemia patients had a history of splenectomy. 27.7% of study patients required hospitalization due to COVID-19 infection. Amongst the hospitalized patients, one patient died (0.7%) and one patient required intubation. Continuous positive airway pressure (CPAP) was required in almost 5% of study patients. After adjustment for age-, sex- and other known risk factors (cardiac disease, kidney disease and pulmonary disease), the rate of in-hospital complications (supplemental oxygen use, admission to the an intensive care unit for CPAP therapy or intubation) and all-cause mortality was significantly lower in the thalassemia group compared to the matched cohort with no history of thalassemia. Amongst thalassemia patients in general, the NTDT group exhibited a higher rate of hospitalization compared to the TDT group (p=0.001). In addition, the rate of complications such as acute kidney injury and need for supplemental oxygen was significantly higher in the NTDT group compared to the TDT group. In the multivariable logistic regression analysis, age and history of heart or kidney disease were all found to be independent risk factors for increased in-hospital, all-cause mortality, whereas the presence of thalassemia (either TDT or NTDT) was found to be independently associated with reduced all-cause mortality. Conclusions: The presence of thalassemia in COVID-19 patients was independently associated with lower in-hospital, all-cause mortality and few in-hospital complications in in our study. The pathophysiology of this is unclear and needs to be studied in vitro and in animal models. Trial Registration for sources of data extraction: NCT: 04334291, 04746066 Funding Statement: This study was funded by a non-conditioned grant from FUNDACION INTERHOSPITALARIA PARA LA INVESTIGACION CARDIOVASCULAR, FIC. (Madrid, Spain). This nonprofit institution had no role in the study design, the collection, analysis and interpretation of data, the writing of the report, or the decision to submit the paper for publication. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: The study was approved by the Ethics Committees in all of the centers involved (Banjarmasin, Bari, Cagliari, Catania, Ferrara, Gela, Genoa, Getafe, Guadalajara, Legan, Madrid, Mannheim, Milan, Monza, Naples, Olbia, Padua, Pavia, Ragusa, Rome, Salerno, Turin, Valladolid and Verona).