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Background: Since December 2019, kidney transplant recipients (KTRs) have experienced a great impact of the coronavirus disease 2019 (COVID-19) pandemic, with a higher risk of morbidity and mortality compared to the general population. Preliminary data in KTRs suggest that the Omicron variant, which has been dominant since December 2021, is more infectious than the previous ones but is associated with reduced risk of severity and low lethality rates. The purpose of our study was to assess the disease course and outcomes of the SARS-CoV-2 infection in KTRs during the Omicron-surge. Methods: This retrospective study included 451 KTRs diagnosed with SARS-CoV-2 infection between 1 December 2021 and 30 September 2022. Demographic and clinical characteristics at the time of infection, vaccination data, treatment, clinical course, and outcomes were recorded and analyzed. Results: Mean age was 51.8 ± 13.7 years with a male predominance (61.2%). The majority (76.1%) were vaccinated with at least three doses of the available mRNA vaccines, although serology revealed low anti-SARS-CoV-2 antibody titers before infection (33 [3.3–1205] AU/mL). Only 6% of the patients experienced moderate–severe disease. Accordingly, there was low prevalence of adverse outcomes, such as SARS-CoV-2-related hospitalization (11.3%) and death (0.9%). Multivariate analysis revealed that only age significantly increased the risk of SARS-CoV-2-related hospitalization. Conclusions: During the Omicron wave, the clinical course of the SARS-CoV-2 infection in KTRs has substantially changed, with lower rates of moderate and severe disease and a low prevalence of adverse outcomes. Prospective clinical trials are warranted to further elucidate the evolving pathogenesis, management, and long-term outcomes of COVID-19 in such high-risk populations.

Due to their higher risk of developing life-threatening COVID-19 disease, solid organ transplant (SOT) recipients have been prioritized in the vaccination programs of many countries. However, there is increasing evidence of reduced immunogenicity to SARS-CοV-2 vaccination. The present study investigated humoral response, safety, and effectiveness after the two mRNA vaccines in 455 SOT recipients. Overall, the antibody response rate was low, at 39.6%. Higher immunogenicity was detected among individuals vaccinated with the mRNA1273 compared to those with the BNT162b2 vaccine (47% vs. 36%, respectively, p = 0.025) as well as higher median antibody levels of 31 (7, 372) (AU/mL) vs. 11 (7, 215) AU/mL, respectively. Among the covariates assessed, vaccination with the BNT162b2 vaccine, antimetabolite- and steroid-containing immunosuppression, female gender, the type of transplanted organ and older age were factors that negatively influenced immune response. Only mild adverse effects were observed. Our findings confirm poor immunogenicity after vaccination, implicating a reevaluation of vaccination policy in SOT recipients.