Impact of COVID-19 pandemic on collection of allogeneic hematopoietic stem cells

Introduction: COVID-19 pandemic brought challenges in the organization of hematopoietic stem cell (HSC) transplantation. Availability of HSCs was decreased due to donor infection and transport limitations. Accordingly, a series of measures was introduced to ensure the protection of patients and donors and availability of transplants during the pandemic. The goal of this study was to show the impact of COVID-19 pandemic on the collection of allogeneic HSCs in University Hospital Centre (UHC) Zagreb. Methods: We conducted a retrospective analysis for the period from March 1, 2020, to June 30, 2021. The data were collected from hospital computer database and meeting reports of the HSC Transplantation Committee of UHC Zagreb. Results: In the reported period peripheral blood stem cells (PBSC) were preferred, except when bone marrow (BM) transplantation was strongly indicated. Allogeneic HSC grafts were cryopreserved before conditioning to ensure availability on the day of transplantation. Thirteen patients were excluded from the program due to COVID-19 infection. HSCs were collected from related and unrelated donors from the Croatian HSC Donor Registry and World Marrow Donor Assocciation for the total of 135 patients. All 17 (12.5%) harvested BM grafts were transplanted. Sixteen patients were transplanted with PBSC instead of BM. Out of the collected PBSC 94.1% were transplanted but in 17 patients transplantations were delayed due to COVID-19 infection of the donor and/or the patient. Of the total 118 PBSC transplants 100 (84.7%) were cryopreserved in 540 cryo bags. Seven (5.9%) cryopreserved grafts have not been infused because of the progression of the main disease (5), COVID-19 infection of the patient (1) and poor product viability (1). Conclusion: COVID-19 pandemic adversely impacted HSC collection and transplantation with many organizational and logistical challenges. Cryopreservation of allogeneic grafts enabled efficient management of the transplantation programs but was accompanied with the risk of not infusing some grafts, which exposed donors to unnecessary risks and increased the cost of treatment.