Convalescent plasma and predictors of mortality among hospitalized patients with COVID-19: a systematic review and meta-analysis.

Background: Plasma collected from recovered patients with COVID-19 (COVID-19 convalescent plasma [CCP]) was the first antibody-based therapy employed to fight the COVID-19 pandemic. While the therapeutic effect of early administration of CCP in COVID-19 outpatients has been recognized, conflicting data exist regarding the efficacy of CCP administration in hospitalized patients.

Objectives: To examine the effect of CCP compared to placebo or standard treatment, and to evaluate whether time from onset of symptoms to treatment initiation influenced the effect.

Data sources: Electronic databases were searched for studies published from January 2020 to January 2024.

Study eligibility criteria: Randomized clinical trials (RCTs) investigating the effect of CCP on COVID-19 mortality in hospitalized patients with COVID-19.

Participants: Hospitalized patients with COVID-19.

Interventions: CCP versus no CCP.

Assessment of risk of bias: Cochrane risk of bias tool for RCTs.

Methods of data synthesis: The random-effects model was used to calculate the pooled risk ratio (RR) with 95% CI for the pooled effect estimates of CCP treatment. The Grading of Recommendations Assessment, Development and Evaluation was used to evaluate the certainty of evidence.

Results: Twenty-seven RCTs were included, representing 18,877 hospitalized patients with COVID-19. When transfused within 7 days from symptom onset, CCP significantly reduced the risk of death compared to standard therapy or placebo (RR, 0.76; 95% CI, 0.61-0.95), while later CCP administration was not associated with a mortality benefit (RR, 0.98; 95% CI, 0.90-1.06). The certainty of the evidence was graded as moderate. Meta-regression analysis demonstrated increasing mortality effects for longer interval to transfusion or worse initial clinical severity.

Conclusions: In-hospital transfusion of CCP within 7 days from symptom onset conferred a mortality benefit.