Differences in COVID-19-related hospitalization burden between kidney transplant recipients and hemodialysis patients vaccinated against COVID-19

Kidney transplant recipients (KTR) and hemodialysis (HD) patients are highly vulnerable to COVID-19. The degree of protection after mRNA vaccination remains uncertain. Observational, prospective cohort (non-probability convenience sample) of adults under care in a Ramón y Cajal University Hospital (29 Feb 2020-30 May 2022) who received mRNA COVID-19 vaccines. Outcomes were ≥1 COVID-19-related hospitalization and ≥1 ICU admission. We fitted multivariable logistic regression models (reporting odds ratios OR with 95% CIs) adjusted for age (years, linear), sex, and number of vaccine doses (0-4); vaccination was summarized as cumulative doses. IPTW was estimated for baseline diagnostics only; negative-binomial models were used as sensitivity analyses. Calendar time/variant epochs were not included. No patient received passive immunization. 810 patients were analysed (KTR = 679; HD = 131). Adjusted odds of hospitalisation were not significantly different between KTR and HD (OR:1.19; 95%CI:0.70-2.01). For ICU admission, the KTR vs HD estimate was imprecise due to very few events (OR:5.48; 95%CI:0.70-43.09). Age increased hospitalisation odds (OR per year:1.02; 95%CI:1.01-1.04). A dose-response pattern was observed: for hospitalisation, the third dose was associated with lower odds (OR:0.40; 95%CI:0.17-0.97) and the fourth dose showed a borderline reduction (OR:0.43; 95%CI:0.18-1.06); for ICU admission, third and fourth doses were associated with markedly lower odds (OR:0.15; 95%CI:0.04-0.54, OR:0.12; 95%CI:0.03-0.47). We found no clear differences between KTR and HD in the odds of COVID-19-related hospitalisation or ICU admission after vaccination. Findings support active surveillance and booster-focused immunisation in both groups. Although passive immunisation was not evaluated, current recommendations suggest selected patients may benefit from it when available.