SynthesisClinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases2023
Clinical outcomes of the severe acute respiratory syndrome coronavirus 2 Omicron and Delta variant: systematic review and meta-analysis of 33 studies covering 6 037 144 coronavirus disease 2019-positive patients.
Synthesis in Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 64 papers, 3 of them syntheses that pooled it.
What it found
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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.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
64 citing papers in PubMed, 3 syntheses or guidelines pooled it, 84 citations in OpenAlex.
- Meta-analysis of Cognitive Function Following Non-severe SARS-CoV-2 Infection.Neuropsychology review · 2025Pooled it
- The impact of SARS-CoV-2 VOCs on clinical outcomes: an overview of reviews.Frontiers in medicine · 2025Pooled it
- Prophylactic-dose direct oral anticoagulants for non-hospitalised people with COVID-19: A meta-analysis of randomised controlled trials.Journal of global health · 2024Pooled it
- Development and validation of a prognostic model based on clinical laboratory biomarkers to predict admission to ICU in Omicron variant-infected hospitalized patients complicated with myocardial injury.Frontiers in immunology · 2024Trial
- Myocardial Injury and Predictors of In-Hospital Mortality in Severe or Critical COVID-19: A Single-Center Observational Cohort Study.Medicina (Kaunas, Lithuania) · 2026Observational
- Preliminary miRNA profiling of plasma from patients infected with distinct SARS-CoV-2 variants.Molecular biology reports · 2026Article
- Characteristics, all-cause healthcare resource utilisation, and costs among high-risk adults with long COVID during Omicron predominance, 2022-2023: a retrospective cohort study using UK primary care data.BMC health services research · 2026Article
- Implementation of wastewater-based epidemiology in a Northern California acute care hospital: a pilot study, June-July 2024.The Journal of hospital infection · 2026Article
- Development and External Validation of a Prognostic Prediction Model for Hospitalization in SARS-CoV-2-Infected Ambulatory Patients.Open forum infectious diseases · 2026Article
- Changes in cardiovascular health and physical functioning in non-hospitalized, adult COVID-19 patients after 3 years of follow-up.Physiological reports · 2026Article
- Observational
- Serum cytokine profiling reveals CXCL10 (IP-10) as a major predictor of severe COVID-19 outcomes in hospitalized patients during the first pandemic wave in Italy.Frontiers in immunology · 2026Article
- The predictive value of hyaluronic acid for the severity and prognosis of COVID-19: a retrospective multicenter cohort study.Annals of medicine · 2025Article
- Chronic respiratory diseases risk during the COVID-19 pandemic: an integrated modelling approach based on hospital records across 30 countries.Population health metrics · 2025Article
- Chemotherapy and anti-CD20 monoclonal antibody impact on SARS-CoV-2 nucleic acid amplification tests in hematologic malignancies: a retrospective study.BMC infectious diseases · 2025Observational
- COVID-19-Related Healthcare Resource Utilisation and Costs in Paediatric Patients in Germany: A Population-Based Study.Advances in therapy · 2025Article
- Differences in the Clinical Course of COVID-19 in Patients Hospitalized in the 2023/2024 and 2024/2025 Seasons.Journal of clinical medicine · 2025Article
- Hybrid B- and T-Cell Immunity Associates With Protection Against Breakthrough Infection After Severe Acute Respiratory Syndrome Coronavirus 2 Vaccination in Avon Longitudinal Study of Parents and Children (ALSPAC) Participants.The Journal of infectious diseases · 2025Article
- In-hospital mortality among children and adults hospitalized with COVID-19 in Africa across pre-delta, delta, and omicron SARS-CoV-2 waves.International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases · 2025Article
- Association of Inhaled Corticosteroid Use with COVID-19 Severity and Hospitalization in Patients With and Without Respiratory Disease.Journal of aerosol medicine and pulmonary drug delivery · 2025Article
4 more citing papers are in PubMed but not listed here.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
13 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundAlthough the SARS-CoV-2 Omicron variant is considered to induce less severe disease, there have been no consistent results on the extent of the decrease in severity.
objectivesTo compare the clinical outcomes of COVID-19-positive patients with Omicron and Delta variant infection. DATA SOURCES: Searches were implemented up to 8 November 2022 in PubMed, Web of Science, BioRvix, and MedRvix. STUDY ELIGIBILITY CRITERIA: Eligible studies were cohort studies reporting the clinical outcomes of COVID-19-positive patients with Omicron and Delta variant infection, including hospitalization, intensive care unit (ICU) admission, receiving invasive mechanical ventilation (IMV), and death.
participantsCOVID-19-positive patients with Omicron and Delta variant infection. ASSESSMENT OF RISK OF BIAS: Risk of bias was assessed employing the Newcastle-Ottawa Scale. METHODS OF DATA SYNTHESIS: Random-effect models were employed to pool the ORs and 95% CIs to compare the risk of clinical outcome. I
resultsA total of 33 studies with 6 037 144 COVID-19-positive patients were included in this meta-analysis. In the general population of COVID-19-positive patients, compared with Delta, Omicron variant infection resulted in a decreased risk of hospitalization (10.24% vs. 4.14%, OR = 2.91, 95% CI = 2.35-3.60), ICU admission (3.67% vs. 0.48%, OR = 3.64, 95% CI = 2.63-5.04), receiving IMV (3.93% vs. 0.34%, OR = 3.11, 95% CI = 1.76-5.50), and death (2.40% vs. 0.46%, OR = 2.97, 95% CI = 2.17-4.08). In the hospitalized patients with COVID-19, compared with Delta, Omicron variant infection resulted in a decreased risk of ICU admission (20.70% vs. 12.90%, OR = 1.63, 95% CI = 1.32-2.02), receiving IMV (10.90% vs. 5.80%, OR = 1.65, 95% CI = 1.28-2.14), and death (10.72% vs. 7.10%, OR = 1.44, 95% CI = 1.22-1.71).
conclusionsCompared with Delta, the severity of Omicron variant infection decreased.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.