Background. Transfusion of convalescent immune plasma (CP) is commonly used in epidemics. Several articles now describe clinical report data of CP for treatment of SARS-CoV-2-induced COVID-19 disease. Methods. A systematic literature review was conducted using the NCBI curated COVID-19 related open-resource literature database LitCovid to identify studies using CP as treatment for COVID-19 patients. We retrieved and curated all COVID-19 related patient and treatment characteristics from previously reported studies. A Poisson model was developed to evaluate the association between age of the patients, older age being the most common risk factor for COVID-19 mortality, and recovery time since CP treatment using data extracted from the literature. Results. From 18,293 identified COVID-19 related articles, we included ten studies reporting results of CP treatment for COVID-19 from a total of 61 patients. Decreased symptoms of severe COVID-19 and clearance of SARS-CoV-2 RNA were the most direct observations. We found that patients over the age of sixty who received CP treatment for COVID-19 had a significantly prolonged recovery estimated by viral clearance (from 10 to 29 days since first dose of CP) compared to younger patients, who recovered from the infection in less than a week after receiving CP treatment. Conclusions. Limited published results on plasma transfusion treatment for COVID-19 disease with concomitant treatments suggest that CP therapy for COVID-19 is well tolerated and effective. First randomized clinical trial results, however, reveal no improvements in recovery time for elderly patients with severe COVID-19 between standard treatment alone and added with convalescent plasma. Accordingly, we argue that older patients may need a significantly longer time for recovery. Further randomized clinical trial data for COVID-19 with rigorous ethical standards is urgently needed.