COVID-19 in Solid Organ Transplant Recipient: Exploring Cumulative Incidence, Seroprevalence and Risk Factors for Disease Severity

SIMPLE SUMMARY: It is still uncertain whether recipients of solid organ transplant (SOT) are at increased risk of SARS-CoV-2 infection and/or poor outcomes due to COVID-19 in comparison to the general population. In this study, we report the cumulative incidence and outcomes of SARS-CoV-2 infection in a cohort of 291 SOT recipients. The COVID-19 cumulative incidence in SOT recipients resulted slightly higher compared to that of age-matched population during the study period. Moreover, the SARS-CoV-2 antibody frequency was around 2.6-fold higher than the incidence of cases who tested positive for SARS-CoV-2 RT-PCR, suggesting that the number of SOT recipients infected with SARS-CoV-2 is likely higher than described. In symptomatic recipients, kidney transplant was associated with a higher risk of developing moderate/critical disease, while common risk factors, including age and comorbidities, resulted less relevant for COVID-19 severity. Due to the high estimated crude mortality, symptomatic SOT recipients should be considered at high risk in case of SARS-CoV-2 infection. ABSTRACT: Background: Solid organ transplant (SOT) recipients may be at increased risk for severe disease and mortality from COVID-19 because of immunosuppression and prolonged end-stage organ disease. As a transplant center serving a diverse patient population, we report the cumulative incidence and outcomes of SARS-CoV-2 infection in our cohort of SOT recipients. Methods: We prospectively included in this observational study SOT recipients with a functioning kidney (n = 201), pancreas ± kidney (n = 66) or islet transplant (n = 24), attending outpatient regular follow-up at the San Raffaele Hospital from February 2020 to April 2021. Antibodies to SARS-CoV-2 were tested in all patients by a luciferase immunoprecipitation system assay. Results: Of the 291 SOT recipients, 30 (10.3%) tested positive for SARS-CoV-2 during the study period and prevalence was not different among different transplants. The SARS-CoV-2 antibody frequency was around 2.6-fold higher than the incidence of cases who tested positive for SARS-CoV-2 RT-PCR. As for the WHO COVID-19 severity classification, 19 (63.3%) SOT recipients were mild, nine (30%) were moderate, and two were critical and died yielding a crude mortality rate in our patient population of 6.7%. Kidney transplant (OR 12.9 (1.1–150) p = 0.041) was associated with an increased risk for moderate/critical disease, while statin therapy (OR 0.116 (0.015–0.926) p = 0.042) and pancreas/islet transplant (OR 0.077 (0.007–0.906) p = 0.041) were protective. Conclusions: The incidence of SARS-CoV-2 infection in SOT recipients may be higher than previously described. Due to the relative high crude mortality, symptomatic SOT recipients must be considered at high risk in case of SARS-CoV-2 infection.