Although 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.
To compare the clinical outcomes of COVID-19 positive patients with Omicron and Delta variant infection.
Searches were implemented up to 8 November 2022 in PubMed, Web of Science, BioRvix, and MedRvix.
Eligible studies were cohort studies reporting the clinical outcomes of COVID-19 positive patients with omicron and delta variant infection, including hospitalization, ICU admission, receiving invasive mechanical ventilation (IMV), and death.
COVID-19 positive patients with Omicron and Delta variant infection.
Assessment of risk of bias: Risk of bias was assessed employing the Newcastle-Ottawa Scale (NOS). Methods of data synthesis: Random-effect models were employed to pool the Odds ratios (ORs) and 95% confidence intervals (CIs) to compare the risk of clinical outcome. I 2 was employed to evaluate heterogeneity between studies.
A 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, compared to 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 positive, compared to 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).