Comparative analysis of the outcomes of COVID-19 between patients infected with SARS-CoV-2 Omicron and Delta variants: a retrospective cohort study

Background The SARS-CoV-2 Omicron variant has replaced the previously dominant Delta variant because of high transmissibility. It is responsible for the current increase in the COVID-19 infectivity rate worldwide. However, studies on the impact of the Omicron variant on the severity of COVID-19 are still limited in developing countries. Here, we compared the outcomes of patients infected with SARS-CoV-2 Omicron and Delta variants and associated with prognostic factors, including age, sex, comorbidities, and smoking. Methods We involved 352 patients, 139 with the Omicron variant and 213 with the Delta variant. The whole-genome sequences of SARS-CoV-2 were conducted using the Illumina MiSeq next-generation sequencer. Results Ct value and mean age of COVID-19 patients were not significantly different between both groups (Delta: 20.35 ± 4.07 vs . Omicron: 20.62 ± 3.75; p =0.540; and Delta: 36.52 ± 21.24 vs . Omicron: 39.10 ± 21.24; p =0.266, respectively). Patients infected with Omicron and Delta variants showed similar hospitalization ( p =0.433) and mortality rates ( p =0.565). Multivariate analysis showed that older age (≥65 years) had higher risk for hospitalization (OR=3.67 [95% CI=1.22-10.94]; p =0.019) and fatalities (OR=3.93 [95% CI=1.35-11.42]; p =0.012). In addition, patients with cardiovascular disease had higher risk for hospitalization (OR=5.27 [95% CI=1.07-25.97]; p =0.041), whereas patients with diabetes revealed higher risk for fatalities (OR=9.39 [95% CI=3.30-26.72]; p =<0.001). Conclusions Our study shows that patients infected with Omicron and Delta variants reveal similar clinical outcomes, including hospitalization and mortality. In addition, our findings further confirm that older age, cardiovascular disease, and diabetes are strong prognostic factors for the outcomes of COVID-19 patients. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Indonesian Ministry of Health and Dr. Sardjito Hospital funded our study. The funders had no role in study design, data collection, and analysis, decision to publish, or manuscript preparation. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Medical and Health Research Ethics Committee, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada/Dr. Sardjito Hospital, Yogyakarta, Indonesia (KE/FK/0563/EC/2020). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript