Administration of antibody-rich convalescent plasma to adult patients hospitalized with COVID-19 who did not require mechanical ventilation was linked to a lower risk of death than transfusion of plasma with lower antibody concentrations, according to a study published today in the New England Journal of Medicine.

Led by researchers at Mayo Clinic in Rochester, Minnesota, the retrospective cohort study used a US-wide registry of adult COVID-19 patients from 680 hospitals and determined the levels, or titers, of anti–SARS-CoV-2 immunoglobulin G (IgG) antibodies in plasma donated by recovered COVID-19 patients and transfused into study participants through Jul 4, 2020. The blood-collection centers, researchers, and study participants were blinded to the antibody concentrations at the time of transfusion.

Among the 3,082 patients included in the analysis, all of whom had at least one risk factor for severe coronavirus outcomes, 830 (26.9%) died. One-hundred-fifteen of 515 patients (22.3%) who received high-titer plasma died within 30 days after transfusion, compared with 549 of 2,006 patients (27.4%) given medium-titer plasma, and 166 of 561 (29.6%) given low-titer plasma.

Of the 3,082 patients, 2,014 did not need mechanical ventilation before plasma transfusion. In this subgroup, 50 of 352 (14.2%) who received high-titer plasma died within 30 days, as did 251 of 1,297 patients (19.4%) who received medium-titer plasma, and 81 of 365 patients (22.2%) given low-titer plasma.

That means that patients not receiving mechanical ventilation given high-titer plasma had a 34% lower risk of death within 30 days of transfusion than those receiving low-titer plasma (relative risk [RR], 0.66).


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