Introduction: Although the SARS-CoV-2 Omicron variant demonstrates lower mortality than previous variants in the general population, its mortality risk in immunocompromised kidney transplant recipients (KTRs) remains concerning. The present study compared Omicronrelated mortality with that of seasonal influenza in KTRs. Methods: Using the National Database of Health Insurance Claims of Japan, we conducted a retrospective cohort study of KTRs diagnosed with COVID-19 during the Omicron period (January 2022-March 2023) or influenza (September 2017-March 2023). The primary outcome was 30-day all-cause mortality. Inverse probability of treatment weighting (IPTW) based on propensity scores was employed to adjust for confounding factors. Subgroup analyses were performed stratified by age groups (20-49, 50-59, 60-69, and 70 years). Results: We identified 6, 488 COVID-19 and 5, 347 influenza cases. After IPTW, the 30-day mortality rates were 1. 2% for COVID-19 and 0. 2% for influenza (hazard ratio HR 4. 07 95% CI 2. 18, 7. 59). In subgroup analyses stratified by age, adjusted HRs were as follows: 20-49 years, not estimable due to sparse events; 50-59 years, 2. 06 (0. 57, 7. 48) ; 60-69 years, 6. 52 (1. 89, 22. 48) ; and 70 years, 3. 93 (1. 62, 9. 54). The adjusted absolute risk differences (excess deaths per 1, 000 patients) were 0. 1, 3. 4, 17. 3, and 35. 0, respectively. Conclusion: In this nationwide study, COVID-19 Omicron variant was associated with significantly higher mortality than influenza in KTRs. Age-stratified analyses demonstrated significantly elevated mortality in patients aged 60 years; however, further investigation is warranted in younger age groups given the limited number of events. I have potential conflict of interest to disclose.
Fujikura et al. (2026) studied this question.