Impact of COVID-19 Pandemic on Global Unrelated Stem Cell Donations in 2020 - Report from World Marrow Donor Association

Introduction: World Marrow Donor Association (WMDA) promotes global collaboration for the benefit of stem cell donors and transplant patients. WMDA activities include recording the number of unrelated hematopoietic stem cell (HSC) donations globally.

Because the COVID-19 pandemic also has an impact on the treatment of patients with other diseases, we hypothesise that it also impacted the practice of unrelated hematopoietic stem cell transplantation (HSCT).

We used the 2020 WMDA data to examine the trends in unrelated HSC donations during the COVID-19 pandemic globally, per continent and per country/region.

Methods: Donor registries (DRs) and cord blood banks (CBBs) from 61 countries participated in the 2020 survey, compared to 59 countries in the 2019. Slight differences in participation between the data sets of 2019 and 2020 do not explain the trends we observe in HSC donations. Country/region-specific COVID-19 data on cases and deaths were obtained from the data repository operated by the Johns Hopkins University Center for Systems Science and Engineering(https://github.com/CSSEGISandData/COVID-19, accessed July 12, 2021); and population data were retrieved from the Worldometer website(https://www.worldometers.info/, accessed July 12, 2021).

Results: HSC donations from unrelated donors (peripheral blood stem cells (PBSC) and bone marrow (BM)) decreased from 20,330 in 2019 to 19,623 in 2020 (-3.5%), compared to an average annual growth rate of 3.9% from 2015 to 2019 (figure 1). The 3.5% decrease is composed of a 29.0% decrease for BM and a 2.6% increase for PBSC, resulting in a drop in the BM share of unrelated HSC donations from 19.3% in 2019 to 14.2% in 2020. The number of cord blood unit (CBU) shipments globally decreased with 3.5% from 2,851 to 2,750. The percentage of national use of HSC products (PBSC and BM) increased from 51.2% to 53.5%.

When considering the continent on which the patient is transplanted (table 1), the change rate of use of HSC donated products in 2020 vs. 2019 ranged from -28.0% in South America to +18.2% in Africa. In absolute numbers, the largest decrease of HSC donations occurred for patients in Asia (n=-485) followed by Europe (n=-205), and the largest increase occurred in North America (n=+88) followed by Oceania (n=+25). The share of HSC donations requiring intercontinental transport decreased from 24.6% in 2019 to 21.9% in 2020.

In terms of the country/region of transplant (table 2), the largest percentage decrease occurred in Colombia (-90,5%) followed by Russia (-55,5%). In absolute numbers, the largest decrease occurred in Turkey (-147), with Japan following (-128, although Japan saw an increase of CBU use of +106). The highest growth rate was observed in Iran (+28,7%), followed by South Africa (+28,2%). In absolute figures, the greatest increase occurred in Italy (+67). The two countries receiving the largest HSC donation numbers showed no major changes versus the previous year: USA: +0.6% (although a decrease for CBU of -21,0% was observed) and Germany: -2.4%.

We did not find any significant correlation between the numbers of COVID-19 cases or COVID-19-related deaths per 1 million inhabitants with the HSC donation numbers (Spearman's r=0.05 for cases and =0.08 for deaths).

Discussion: The decline in the number of unrelated HSC donations in 2020 suggests an impact of the COVID-19 pandemic on HSC donation and unrelated HSCT.

The significant decrease in BM collections and intercontinental/cross-border shipments can be explained by logistically complex processes, as well the increased risk to the donor of being exposed to an operative procedure. CBU as a stem cell source potentially circumvents these logistical complications. However, on a global scale our data does not show increased use of CBU suggesting that decisions to use CBU as a stem cell source did not change in the pandemic .

We were unable to demonstrate a correlation between country/region-specific severity of the pandemic and HSC donation numbers. We suspect this is due to the data quality of reported number of COVID-19 cases and COVID-19-related deaths. Also, we did not gather monthly data and therefore could not specify pandemic waves.

In conclusion, we would like to point out the fact that global exchanges of HSC products continued and only decreased slightly is an extraordinary achievement of DRs, CBBs and their donors and is a testament to the importance of international collaborations in the WMDA.

Figure 1

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Figure 1

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