Observational studyRespiratory medicine and research2023
Impact of SARS-CoV-2 Omicron and Delta variants in patients requiring intensive care unit (ICU) admission for COVID-19, Northern Italy, December 2021 to January 2022.
Observational study in Respiratory medicine and research, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 12 papers, 1 of them a synthesis that pooled it.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
12 citing papers in PubMed, 1 synthesis or guideline pooled it.
- The impact of SARS-CoV-2 VOCs on clinical outcomes: an overview of reviews.Frontiers in medicine · 2025Pooled it
- Omicron infection alters the profile of organ failure in severe COVID-19: a multicenter study comparing Omicron and the wild-type strain.BMC infectious diseases · 2026Observational
- Clinical manifestations and severity of COVID-19 caused by Omicron among paediatric patients aged 0-17 years in Italy.Scientific reports · 2025Article
- Persistent mortality in critical COVID-19 ICU cases from wild-type to delta variant: A descriptive cohort study.Scientific reports · 2025Observational
- SARS-COV-2 causes significant abnormalities in the fibrinolysis system of patients: correlation between viral mutations, variants and thrombosis.Frontiers in cellular and infection microbiology · 2025Article
- A tri-light warning system for hospitalized COVID-19 patients: Credibility-based risk stratification for future pandemic preparedness.European journal of radiology open · 2024Article
- Impact of corticosteroid doses on prognosis of severe and critical COVID-19 patients with Omicron variant infection: a propensity score matching study.Inflammopharmacology · 2024Article
- Assessing the impact of Delta and Omicron in German intensive care units: a retrospective, nationwide multistate analysis.BMC health services research · 2024Article
- Risk of intensive care unit admission and mortality in patients hospitalized due to influenza A or B and SARS‑CoV‑2 variants Omicron or Delta.Immunity, inflammation and disease · 2024Article
- Investigation of Initial Viral Loads and Patient Characteristics as Predictors of COVID-19 Outcomes: A Retrospective Cohort Study.Infectious disease reports · 2023Article
- Comparison of SARS-Cov-2 omicron variant with the previously identified SARS-Cov-2 variants in Egypt, 2020-2022: insight into SARS-Cov-2 genome evolution and its impact on epidemiology, clinical picture, disease severity, and mortality.BMC infectious diseases · 2023Article
- SARS-CoV-2 Omicron variant infection affects blood platelets, a comparative analysis with Delta variant.Frontiers in immunology · 2023Article
Corrections and comments
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Authors and funding
61 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
This multicenter observational study included 171 COVID-19 adult patients hospitalized in the ICUs of nine hospitals in Lombardy (Northern Italy) from December, 1st 2021, to February, 9th 2022. During the study period, the Delta/Omicron variant ratio of cases decreased with a delay of two weeks in ICU patients compared to that in the community; a higher proportion of COVID-19 unvaccinated patients was infected by Delta than by Omicron whereas a higher rate of COVID-19 boosted patients was Omicron-infected. A higher number of comorbidities and a higher comorbidity score in ICU critically COVID-19 inpatients was positively associated with the Omicron infection as well in vaccinated individuals. Although people infected by Omicron have a lower risk of severe disease than those infected by Delta variant, the outcome, including the risk of ICU admission and the need for mechanical ventilation due to infection by Omicron versus Delta, remains uncertain. The continuous monitoring of the circulating SARS-CoV-2 variants remains a milestone to counteract this pandemic.
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