SARS-CoV-2 Omicron Infections among Vaccinated Maintenance Hemodialysis Patients: Outcomes and Comparison to Delta Variant.

Background: Infections with B.1.1.529 (Omicron) variants of SARS-CoV-2 became predominant worldwide since late 2021, replacing the previously dominant B.1.617.2 variant (Delta). While those variants are highly transmissible and can evade vaccine protection, population studies suggested that outcomes from infection with Omicron variants are better compared with Delta. Data regarding prognosis of maintenance hemodialysis (MHD) patients infected with Omicron versus Delta variants, however, are scarce.

Methods: This retrospective cohort study includes all patients with end-stage kidney disease treated with MHD in Meir Medical Center, Kfar-Saba, Israel, that were diagnosed with SARS-CoV-2 infection between June 2021 and May 2022.

Results: Twenty-six subjects were diagnosed with the Delta variant and 71 with Omicron. Despite comparable age between groups and higher mean vaccine doses prior to the infection among the Omicron group (p < 0.001), SARS-CoV-2 infection severity was significantly worse among MHD infected with the Delta variant: 50% developed severe or critical COVID-19 versus 5% in the Omicron group (p < 0.001). Over half of MHD infected with Omicron (57%) were asymptomatic during their illness. The 30-day mortality rate for the whole cohort was 5.2%. It was significantly higher among MHD in the Delta group than in the Omicron group (5/26, 19.2% vs. 0/71, p < 0.001), as was the 90-day mortality rate (5/26, 19.2% vs. 3/71, 4.2%, p = 0.02).

Conclusions: Infection with the SARS-CoV-2 Delta variant was associated with worse outcomes compared with Omicron, among subjects on MHD. However, despite mild disease among vaccinated MHD patients, infection with Omicron variant was still associated with the significant 90-day mortality rate.