COVID-19 and solid organ transplantation: Finding the right balance

BACKGROUND: The COVID-19 pandemic has a great impact on solid organ transplant (SOT) recipients due to their comorbidities and their maintenance immunosuppression. So far, studies about the different aspects of the impact of the pandemic on SOT recipients are limited. OBJECTIVES: This systematic review summarizes the risk factors that make SOT patients more vulnerable for severe COVID-19 disease or mortality and the impact of immunosuppressive therapy. Furthermore, their clinical outcomes, mortality risk, immunosuppression, immunity and COVID-19 vaccination efficacy are discussed. METHODS: A systematic search on PubMed was performed to select original articles on SOT recipients concerning the following four topics: (1) mortality and clinical course; (2) risk factors for mortality and composite outcomes; (3) maintenance immunosuppression; (4) immunity to COVID-19 infection and (5) vaccine immunogenicity. Relevant data were extracted, analyzed and summarized in tables. RESULTS: This systematic review includes 77 articles. Mortality was associated with advanced age. Post-transplantation time or comorbidities were variably identified as independent risk factors for mortality or severe disease. However, generally, no comorbidity was reported as a major risk factor. SOT recipients have a higher risk of acute kidney injury, but no higher rate of mortality compared to non-transplanted patients was found. Immunosuppression was individually adjusted, without leading to high rates of graft dysfunction. Generally, no association between type of immunosuppression and mortality was found. SOT patients established humoral and cellular immune responses after COVID-19 disease comparable to immunocompetent people. At last, SOT patients experience a diminished immune response after two-dose vaccination with SARS-COV-2-mRNA-vaccines. CONCLUSION: More research is needed to address the direct effect of COVID-19 disease on the graft in lung transplant recipients, as well as the factors ameliorating the immune response in SOT recipients.