the SARS-CoV2 pandemic has led to a major reorganization of the French Hematology and stem cell transplant departments since march 2020. Since the allogeneic stem cell transplant cannot be delayed especially when patients with hematological malignancies are in a fragile remission, risking relapse at any time, the necessity to maintain safe hematopoietic stem cell (HSC) donations from match unrelated or family donors appears rapidly mandatory during the pandemic period. To increase the safety of voluntary donations, a SARS-CoV2 Polymerase Chain Reaction test has been recommended to donors by regulatory agencies. However, due to the lack of homogeneity of care at European level, some countries do not require SARS-CoV-2 testing in asymptomatic donors. In this case, the test is performed on additional EDTA tube accompanying the graft on arrival or in the case of a missing tube (not collected or forgotten), on few milliliters of the HSC graft. This circuit had the consequence of forcing the clinicians to wait for the test result before starting the patient's conditioning regimen. The graft being already collected and received at the transplant center, and the conditioning regimen lasting on an average of 5 days, this resulted in its conservation during this minimum period and therefore its freezing by the associated cell therapy unit. However, this practice has so far been exceptional regarding allogeneic transplants, which are primarily freshly infused to ensure to the recipient the highest viability and functionality of stem cells. Since the entire freezing-thawing and washing process may impact cell viability and delay the patient's aplastic recovery, this study aimed to analyze the results of one year of allogeneic transplants infused after freezing in terms of graft quality after thawing and clinical consequences.

Inclusion Criteria:

• patients receiving an allogeneic stem cell transplant between march 2020 and may 2021.

Exclusion Criteria:

• patients receiving an allogeneic stem cell transplant before march 2020 and after may 2021.

Patients (children and adults) having HSCT and treated at the CHRU of NANCY between march march 2020 to may 2021