Impact of COVID-19 on Recipients of Solid Organ Transplants: A Cohort Study of In-Hospital Outcomes From the Canadian Organ Replacement Register

Background: Solid organ transplant (SOT) recipients in Canada are particularly vulnerable to adverse hospital outcomes, especially during admissions involving a COVID-19 diagnosis. Limited evidence exists regarding how risks vary across different organ types and the extent to which a COVID-19 diagnosis influences hospital outcomes. This study aims to examine the association of organ subtypes on hospital morbidity and mortality, both in the presence and absence of a COVID-19 diagnosis in a large, nationally representative Canadian cohort. Methods: We used data from the Canadian Organ Replacement Register and the Discharge Abstract Database to examine hospitalization rates and in-hospital outcomes among all available adult SOT recipients with functioning grafts in Canada (excluding Quebec and Manitoba) from January 2021 to December 2022. In-hospital outcomes included transfer to a special care unit (SCU) and hospital mortality. Comparisons between organ subtypes (kidney, liver, heart, lung, and other/multi-organ) were conducted separately for admissions with and without a diagnosis of COVID-19, using kidney transplant (KT) recipients as the reference group. We included all admissions with a COVID-19 diagnosis irrespective of whether it was the primary reason for admission or not. Rates of hospitalization, SCU transfer, and mortality were analyzed using negative binomial or Poisson regression models (adjusted for age and sex) and reported using incidence rate ratios (IRRs) with 95% confidence intervals (CIs). Results: Among 23 497 SOT recipients, the majority (14 628, 62%) were KT recipients. Within this cohort, 2428 individuals (10.3%) experienced a total of 2925 hospitalizations with a COVID-19 diagnosis. In comparison, 7808 (33.2%) individuals experienced 17 656 hospitalizations without a COVID-19 diagnosis. Lung transplant recipients were more likely to be hospitalized (IRR = 1.65, 95% confidence interval CI: 1.52-1.80) and die in hospital (IRR = 1.2, 95% CI: 1.05-1.34) than KT recipients during admissions involving a COVID-19 diagnosis. In contrast, heart and liver transplant recipients were less likely to be hospitalized or experience a poor outcome. For hospitalizations without a COVID-19 diagnosis, lung and other/multi-organ transplant recipients were more likely than KT recipients to be hospitalized (IRR = 1.94, 95% CI: 1.76-2.15; IRR = 1.81, 95% CI: 1.45-2.26, respectively), transferred to an SCU (IRR = 1.89, 95% CI: 1.58-2.27; IRR = 1.81, 95% CI: 1.45-2.26, respectively), and die in hospital (IRR = 2.04, 95% CI: 1.84-2.27; IRR = 1.57, 95% CI: 1.33-1.85; respectively). Conclusion: SOT recipients in Canada, especially lung transplant recipients, experience high rates of hospitalization, SCU admission, and in-hospital mortality. Notable differences observed between organ subtypes for admissions with and without a COVID-19 diagnosis may reflect differences in immunosuppressive medication regimens, informing areas for future research.