#1742 Hybrid-immunity protection against SARS-CoV-2 reinfection on kidney transplant recipients

Background and Aims Scarce data is available about the impact of hybrid immunity (vaccination plus infection) in immunocompromised patients. Several studies report a greater immunological response in hybrid individuals compared to those who are vaccinated-only, but no study has evaluated its clinical implication. We aimed to investigate the protection of hybrid immunity against SARS-CoV-2 infection, relative to the vaccine-only acquired immunity in a population of kidney transplant recipients over a omicron SARS-CoV-2 wave. Method This observational retrospective cohort study was done on kidney transplant recipients vaccinated with three or four doses against SARS-CoV-2, at Bellvitge University Hospital, Spain. All participants were interviewed to ascertain if they have suffered a natural infection. Data was also obtained from clinical records database of our institution and the Catalan Transplant Organisation. Incidence of SARS-CoV-2 infection and COVID-related hospitalisation and death in the hybrid cohort was compared with the incidence in the vaccine cohort, using Cox proportional hazard regressions models. Results 1338 kidney transplant recipients participated in the study, 544 (40.7%) out of them were hybrid at the start of the study. 341 infections, 46 hospitalisations and 14 deaths were recorded during follow-up. The overall adjusted hazard ratio for SARS-CoV-2 infection was 0.30 (95% CI 0.23-0.40) and 0.11 (95% CI 0.03-0.35) for hospitalization in the hybrid cohort versus the vaccine cohort. No death occurred in the hybrid cohort during the follow-up. Conclusion Hybrid immunity was associated with a lower incidence of SARS-CoV-2 infection and COVID-19 related hospitalisation. Hybrid immunity should be considered when stratifying the risk of SARS-CoV-2 infection and progression to severe COVID-19 in immunocompromised individuals, in order to better adjust immunosuppression, guide booster policies and prioritize outpatient treatments.