**1. Introduction**

The coronavirus disease 2019 (COVID-19) is a respiratory and systemic disease caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). SARS-CoV-2 can infect multiple organs, including lungs, heart, liver, and kidney [1].

Several risk factors are associated with an increased risk for severe COVID-19, such as respiratory disorders [2] and metabolic diseases [3]. Transplantation is an established treatment for end-stage organ diseases, and patients commonly receive immunosuppressive therapy to prevent organ rejection [4]. There is conflicting data in the literature regarding the impact of COVID-19 on solid organ transplant (SOT) recipient patients. Some reports suggest that immunosuppressive therapy reduces the severity of the COVID-19-associated inflammation, while other reports did not observe such an effect, reporting similar inflammation to non-SOT patients [5–8]. Previous reports have identified increased lethality in

**Citation:** Alberca, R.W.; Alberca, G.G.F.; Netto, L.C.; Orfali, R.L.; Gozzi-Silva, S.C.; da Silva Duarte, A.J.; Aoki, V.; Sato, M.N.; Benard, G. COVID-19 Severity and Mortality in Solid Organ Transplantation: Differences between Liver, Heart, and Kidney Recipients. *Transplantology* **2021**, *2*, 296–303. https://doi.org/ 10.3390/transplantology2030030

Academic Editors: Macé M. Schuurmans and René Hage

Received: 15 July 2021 Accepted: 17 August 2021 Published: 18 August 2021

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SOT recipients, comparing the survival rate with that of the general population, which could be influenced by the difference in treatments and associated comorbidities [9]. A case-controlled study concluded that SOT patients were not at greater risk during COVID-19, the immunosuppressive treatment did not influence the outcome of COVID-19 [10], and SOT patients did not present an increase in respiratory failure or cytokine production [11].

The SOT recipients may also respond differently to COVID-19 due to associated comorbidities, drugs used to prevent organ rejection, or the organ transplanted [12]. The prevalence of SOT patients varies among COVID-19 reports, which could be affected by the susceptibility to SARS-CoV-2 or the general prevalence of those patients in the population [13].

Several case reports have investigated the COVID-19 outcome in solid organ transplant recipients. Nevertheless, no longitudinal comparison between different organ recipients has been made to this moment. Therefore, we performed a longitudinal investigation on COVID-19 course and survival analysis in SOT patients (recipients of heart, kidney, and liver) with over one and a half years post transplant, in a single-center investigation during the same period.
