Introduction: The COVID-19 pandemic is still affecting the World. According to the Centers for Disease Control and Prevention, solid organ transplant (SOT) recipients are among those at high risk of serious illness from SARS-CoV-2. Because of the virus's novelty, there is still a lack of information on topics such as how it behaves in immunocompromised hosts, how it affects immunosuppression, how it affects rejection, and whether it increases the incidence of opportunistic infections. In this study, we aimed to evaluate the clinical course of SOT recipients with COVID-19 over a one year follow-up period and to evaluate co- infections or secondary infections.

Method: Data from SOT patients diagnosed with COVID-19 has been retrieved retrospectively from the hospital information management system since March 2020. Demographic characteristics, examinations during hospitalization and admissions to outpatient clinics after illness were screened in detail.

Results: There were 53 SOT patients recorded. The median age was 49, the median time post-transplant was 11 years, thirty-four (71.7 %) were men. The kidney was the most frequently transplanted organ (75.5 %). Severe/critical COVID-19 was diagnosed within 11 (20.8%) patients. The most common symptoms were fever (49.1%) and cough (39.6%). Thirty-nine (73.6 %) of the patients were hospitalized. Among those 14 (26.4%) required mechanical ventilation, 8 (15%) required renal replacement therapy, and five (9.4%) died 7 days after diagnosis, 10 (18.8%) patients died 30 days after diagnosis. Co-infections occurred in 15 patients; there were six urinary tract infections, four bacteremia, two Cytomegalovirus (CMV), and one both with CMV and a urinary tract infection. During the follow-up, CMV and Aspergillosis were both detected in three patients, only CMV in one, only Aspergillosis in one, a healthcare-associated infection in one, and pancreatitis in one. All patients who developed CMV and/or aspergillosis had been given high dose steroid during their COVID-19 treatment. Two (3.7%) patients had acute rejection during this period.

Conclusion: The impact of immunosuppression on COVID-19 disease severity remains unclear. We believe that high-dose steroid therapy aids SOT patients who develop opportunistic infections such as CMV and aspergillosis. According to some studies, high-dose steroid therapy used to treat COVID-19 can cause opportunistic infections. In our study, we believe that the mortality rates were high due to our patients' long post-transplantation period and, as a result, their chronic immunosuppression status. Wide-range studies are required to assess the long-term outcomes including allograft rejection, co-infections and secondary infections in SOT patients.