No Negative Impact Associated With Blood Products Transfused from COVID-19-Vaccinated Donors

Transfusion of plasma and platelet components collected from donors who were previously infected with or vaccinated against COVID-19 was not associated with an increased risk for adverse events or poor outcomes in COVID-19-negative transfusion recipients, according to new findings published in Transfusion. The study also demonstrated that transfusing these components was not associated with worsened outcomes among several different patient subgroups, including unvaccinated transfusion recipients.

In the retrospective cohort study, a team of investigators led by the Kaiser Permanente Division of Research examined whether transfusing these components during periods of rising COVID-19 infection and vaccination affected patient outcomes. The team compared rates of thrombotic or pulmonary events, ICU length of stay, hospital mortality and rehospitalization among 18,584 patients without COVID-19 who received a plasma or platelet transfusion before the pandemic, before the introduction of COVID-19 vaccines and after the introduction of COVID-19 vaccines.

Among 21,750 total hospitalizations, 10,317 involved transfusions of only platelet components, 7,676 involved only plasma components and 3,757 involved both platelet and plasma components. Among all transfused patients, investigators found no trends in unadjusted or adjusted rates of thromboses (OR 0.9 [95% CI 0.8, 1.1]; p = .22) or increased oxygen requirements (OR 1.0 [95% CI 0.9, 1.1]; p = .41) in plasma and platelet product recipients during known periods of increasing blood donor COVID-19 infection and vaccination. Additionally, the researchers did not identify changes in ICU length of stay (p = .83), adjusted hospital mortality (OR 1.0 [95% CI 0.9–1.0]; p = .36) or rehospitalization across the study periods (p = .29).

In addition, the investigative team compared outcomes between COVID-19-vaccinated and unvaccinated recipients during the post-vaccine period. They found no differences in rates of thromboses (3.6% versus 4.1%; p = .46) or oxygen requirements (10.9% versus 10%; p = .35) between these two groups. There were also no trends across study periods for adjusted hospital mortality among unvaccinated recipients (OR, 1.0 [CI, 0.9 to 1.0]; p = .49).

According to investigators, the findings for unvaccinated transfusion recipients are particularly notable because some recipients of blood products have expressed concern about the passive transfer of COVID-19 antigens or antibodies. These findings were consistent with clinical trial and observational data supporting the safety of COVID-19 convalescent plasma (CCP) and laboratory-based studies that did not find evidence of an impact of CCP transfusion on the adaptive immune response of recipients.

The investigators concluded that the findings are “reassuring for both clinicians and professionals involved in blood banking” and do not indicate any changes are necessary to current transfusion practice. However, they did acknowledge limitations in the study to be addressed in future research. Specifically, investigators were unable to examine direct relationships between blood donor antibody titers and outcomes in transfusion recipients and, therefore, may not be able to detect rare adverse effects. Additional analysis will link transfusion of plasma-containing blood products with donor SARS-CoV-2 spike and nucleocapsid antibody results, along with survey data on donor infection and vaccination, to help answer blood safety questions about the timing of blood donation after COVID-19 infection or vaccination.