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.