COVID-19 among kidney transplant recipients: evaluating risk factors during the initial phase of the pandemic.

Background: Current knowledge about risk factors for severe COVID-19 among kidney transplant recipients stem from meta-analyses of small or regional studies.

Methods: All kidney transplant recipients in Sweden as of 1 January 2020 (n = 5824) were followed during the first 2 years of the pandemic. Data from the Swedish Renal Registry and linked health care registries were analyzed by multivariable adjusted logistic regression to identify risk factors for severe COVID-19, defined as hospitalization or death due to COVID-19.

Results: Male sex increased the risk of severe COVID-19. While many comorbidities were associated with increased risk, their significance diminished after adjustment for other factors. Kidney transplant recipients of working age, 49-58 years adjusted odds ratio (aOR) 2.32 (95% CI 1.53-3.51) and 59-68 years aOR (1.92; 1.26-2.91) had the highest risk compared to the youngest age group (18-38 years). Compared to recently (<1 year) transplanted patients, those transplanted >5 years ago had a lower risk of severe COVID-19 (aOR 0.52; 0.36-0.75 for 6-10 years; aOR 0.57; 0.41-0.79 for >10 years). Longer pre-transplant dialysis vintage (aOR_1-year 1.04; 1.01-1.06) and deceased donor kidneys (aOR 1.41; 1.09-1.84) increased the risk. Immunosuppression with mycophenolate mofetil (aOR 1.47, 95% CI 1.08-1.99) and proton pump inhibitor use (aOR 1.58, 95% CI 1.24-2.01) were strongly associated with severe COVID-19.

Conclusions: While kidney transplant recipients share risk factors with the general population, working age groups were at the highest risk, unlike in the general population. These findings emphasize the need for targeted prevention and treatment strategies for kidney transplant recipients in future pandemics.