Convalescent Plasma Therapy in COVID-19 Management

Convalescent plasma therapy has been explored as a means of delivering passive immunity to patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. By transfusing plasma from individuals who have recovered from COVID-19, high concentrations of polyclonal antibodies are introduced to neutralise circulating virus and modulate the host inflammatory response. Early in the pandemic, clinicians deployed convalescent plasma in the absence of specific antivirals or monoclonal antibodies. Results have varied markedly, reflecting differences in patient populations, timing of administration, antibody titre and plasma antibody profile. While some observational studies suggested reductions in viral load and clinical improvement, large-scale trials in hospital settings have largely failed to demonstrate a survival benefit. Subgroup analyses indicate that convalescent plasma may be most effective when administered at an early stage of infection—before endogenous humoral responses have matured—or in immunocompromised individuals incapable of mounting an adequate antibody response. Recent work has also highlighted potential complications associated with certain plasma antibody profiles, including immune complex–mediated coagulopathy. Logistics of donor selection, plasma collection and standardisation of antibody potency remain critical. Globally, convalescent plasma continues to be considered for vulnerable populations and in regions where access to novel therapeutics is limited.

Research from Nature Portfolio

Recent randomised trials have examined the clinical utility of convalescent plasma in hospitalised patients receiving oxygen support. In one open-label study, allocation to high-titre plasma did not reduce the composite endpoint of intubation or death by 30 days compared with standard care. Analyses revealed that functional characteristics of donor antibodies modulated outcomes: greater neutralising capacity and antibody-dependent cellular cytotoxicity were associated with reduced risk, whereas elevated full-spike IgG levels correlated with worse outcomes. These findings underscore the importance of characterising antibody profiles beyond simple titre measurements.

In a parallel translational investigation, researchers conducted a comprehensive virological and immunological assessment of plasma therapy in severe COVID-19 patients. The majority presented with potent neutralising antibodies at admission, equivalent to those of carefully selected plasma donors. Convalescent plasma did not enhance viral clearance, alter cytokine responses or improve survival. The trial was terminated early for futility, with the study advocating for administration at an earlier disease stage, prior to the development of autologous humoral immunity.

Convalescent Plasma Therapy in COVID-19 Management publication trend

The graph below shows the total number of articles in convalescent plasma therapy in covid-19 management across all publications each year (not limited to Nature Index journals).

Technical terms

Convalescent plasma (CP): Plasma collected post-recovery containing polyclonal antibodies against SARS-CoV-2.

Neutralising antibody titre: Quantitative measure of plasma dilution required to inhibit viral infectivity.

Antibody-dependent cellular cytotoxicity (ADCC): Mechanism by which antibodies direct immune cells to destroy virus-infected targets.

D-dimer: Fibrin degradation fragment indicating activation of coagulation and thrombotic risk.

References

1. Post-transfusion activation of coagulation pathways during severe COVID-19 correlates with COVID-19 convalescent plasma antibody profiles. Journal of Clinical Investigation (2025).
2. Early, very high-titre convalescent plasma therapy in clinically vulnerable individuals with mild COVID-19: an international, randomised, open-label trial. EBioMedicine (2025).
3. Convalescent plasma for hospitalized patients with COVID-19: an open-label, randomized controlled trial. Nature Medicine (2021).
4. Effects of potent neutralizing antibodies from convalescent plasma in patients hospitalized for severe SARS-CoV-2 infection. Nature Communications (2021).