Background 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. Objectives To 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. Participants 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. Methods of data synthesis Random-effect models were employed to pool the ORs and 95% CIs to compare the risk of clinical outcome. I^{2} was employed to evaluate the heterogeneity between studies. Results 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 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). Conclusions Compared with Delta, the severity of Omicron variant infection decreased.
【저자키워드】 Meta-analysis, SARS-CoV-2, Hospitalization, Delta, omicron,