SARS-CoV-2 antibody changes in patients receiving COVID-19 convalescent plasma from normal and vaccinated donors

Leon, J.; Merrill, A.; Rogers, K.; Kurt, J.; Dempewolf, S.; Ehlers, A.; Jackson, B.; Knudson, M.

Background and Objectives: Vaccination has been shown to stimulate remarkably high antibody levels in donors who have recovered from COVID-19. Our objective was to examine patient antibody responses following COVID-19 Convalescent Plasma (CCP) transfusion and compare responses to CCP from vaccinated and nonvaccinated donors. Materials and methods: Plasma samples were obtained from 25 recipients of CCP and COVID-19 antibody levels measured before and after CCP treatment. Factors that effect antibody levels were examined. Results: In the 21 patients who received CCP from nonvaccinated donors, only modest increases in antibody levels were observed. Patients who received two units were more likely to seroconvert than those receiving just one unit. The strongest predictor of changes in patient antibody level was the CCP dose. Using patient plasma volume and donor antibody level, the post-transfusion antibody level could be predicted with remarkable accuracy. In contrast, the 4 patients who received CCP from vaccinated donors all had dramatic increases in antibody levels following transfusion of a single unit. In this subset of recipients, antibody levels observed after transfusion of CCP were comparable to those seen in donors who had fully recovered from COVID-19. Conclusion: If available, CCP from vaccinated donors with very high antibody levels should be used. CCP from vaccinated donors increases patient antibody levels much more than 1 or 2 units of CCP from unvaccinated donors.