To explore whether convalescent plasma therapy is beneficial to patients with severe acute respiratory infections and gave hints to the management of COVID-19.

A comprehensive literature search of PubMed, Web of Science, Embase, and Cochrane library was conducted for all eligible studies range from inception to February 29, 2020. Studies with control group were included. Treatment group received convalescent plasma therapy, and control group may receive any therapy other than convalescent plasma therapy. Odds ratios (ORs), mean differences (MDs) and 95% confidence intervals (CIs) were pooled for categorical and continuous outcomes.

A total of 1997 patients from 13 studies were included, and seven studies were prospectively designed. Pooled analysis indicated convalescent plasma treatment significantly reduced the mortality by 51% (OR=0.49, 95% CI: 0.36 to 0.67). Subgroup analyses by publication time, study design, and influenza A revealed similar results. Sensitivity analyses suggested that the results were stable. In addition, convalescent plasma therapy reduced mechanical ventilation requirement (OR: 0.35, 95% CI: 0.21 to 0.59), while it was not associated with less use of extracorporeal membrane oxygenation (OR: 2.0, 95% CI: 0.83 to 4.83) and shorter length of hospital stay (MD: −2.20, 95% CI: −4.98 to 0.57days). Pooled estimates showed there was no difference in serious adverse effects between the convalescent plasma treatment and control groups (OR: 0.75, 95% CI: 0.50 to 1.13).

Convalescent plasma therapy significantly reduced the mortality and mechanical ventilation requirements of patients with virus-induced severe acute respiratory infections, without serious adverse effects. More studies are needed to explore whether this treatment can be extrapolated into COVID-19.