Convalescent plasma therapy in COVID-19 patients: a non-randomized case-control study with concurrent control

Convalescent plasma therapy has shown controversial results in coronavirus disease-19 (COVID-19) patients. We performed a non-randomized case-control study with contemporaneous controls in a hospital in southern Brazil. Patients were selected for treatment with convalescent plasma by medical decision and compared with patients who did not receive plasma and were hospitalized due to COVID-19 at the same time. The outcomes of interest were intensive care unit (ICU) admission and in-hospital death. Patients that received convalescent plasma had lower in-hospital mortality than patients that did not receive plasma (relative risk (RR) 0.48; 95% confidence interval (CI) 0.29 to 0.79) and these results were consistent after changing the subset of control patients. There were no differences regarding ICU admission between groups (RR=0.80; 95%CI: 0.47 to 1.35). In this study, patients that received convalescent plasma for COVID-19 had lower in-hospital mortality, but this finding requires further confirmation given the retrospective nature of the study.