Effects of potent neutralizing antibodies from convalescent plasma in patients hospitalized for severe SARS-CoV-2 infection

In a randomized clinical trial of 86 hospitalized COVID-19 patients comparing standard care to treatment with 300 ml convalescent plasma containing high titers of neutralizing SARS-CoV-2 antibodies, no overall clinical benefit was observed. Using a comprehensive translational approach, we unravel the virological and immunological responses following treatment to disentangle which COVID-19 patients may benefit and should be the focus of future studies. Convalescent plasma is safe, does not improve survival, has no effect on the disease course, nor does plasma enhance viral clearance in the respiratory tract, influence SARS-CoV-2 antibody development or serum proinflammatory cytokine levels. We show that the vast majority of patients already had potent neutralizing SARS-CoV-2 antibodies at hospital admission with titers comparable to carefully selected plasma donors. This led to premature termination of the trial. Treatment with convalescent plasma should be studied early in the disease course or at least before autologous humoral response development.