Convalescent plasma (CP) has been used successfully to treat many types of infectious disease, and has shown initial effects in the treatment of the emerging 2019 coronavirus disease (COVID-19). However, its curative effects and feasibility have yet to be confirmed by formal evaluation and well-designed clinical trials. To explore the effectiveness of treatment and predict the potential effects of CP with COVID-19, studies of different types of infectious disease treated with CP were included in this systematic review and meta-analysis.

Related studies were obtained from databases and screened according to the inclusion criteria. The data quality was assessed, and the data were extracted and pooled for analysis.

40 studies on CP treatment for infectious diseases were included. Our study found that CP treatment could reduce the risk of mortality, with a low incidence of adverse events, promote the production of antibodies, lead to a decline in viral load, and shorten the disease course. A meta-analysis of 15 controlled studies showed that there was a significantly lower mortality rate in the group treated with CP (pooled OR = 0.32; 95% CI = 0.19–0.52; p < 0.001, I² = 54%) compared with the control groups. Studies were mostly of low or very low quality, with a moderate or high risk of bias. The sources of clinical and methodological heterogeneity were identified. The exclusion of heterogeneity indicated that the results were stable.

CP therapy has some curative effect and is well tolerated in treating infectious diseases. It is a potentially effective treatment for COVID-19.