Impact of COVID-19 Vaccination on the Mortality Rates of Hospitalized Patients with the Omicron Strain

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Background: The emergence of the Omicron variant of the SARS-CoV-2 virus has raised concerns about its potential impact on public health. Vaccination remains crucial for preventing and managing the spread of COVID-19, as well as for mitigating future outbreaks of similar diseases. This study aimed to evaluate the impact of COVID-19 vaccination on the mortality rates of hospitalized patients infected with the Omicron strain. We sought to provide valuable insights into vaccine efficacy and inform public health strategies. Objectives: To determine the effectiveness of vector-based and non-vector-based vaccines on the mortality rate of hospitalized patients infected with the COVID-19 Omicron strain and related variants, considering factors such as age, gender, symptom onset-to-hospitalization days, oxygen saturation level, hospital stay length, and underlying diseases. Methods: A cross-sectional study was conducted on patients from hospitals affiliated with Mashhad University of Medical Sciences, Mashhad, Iran, from January 2021 to September 2022. Data were collected from the medical care monitoring system (MCMC), continuously updated from six medical universities. The study included 8,616 COVID-19 patients admitted to these hospitals. Vaccination status (vector-based and non-vector-based) and its association with Omicron variant infection were assessed using logistic regression analysis. Results: Among the 8,616 hospitalized patients, 50% were men and 50% were women. Twenty-three percent of cases had a history of hypertension, and 15% had diabetes mellitus. In elderly hospitalized patients, the mortality rate related to COVID-19 increased significantly (16% in those over 70 years old). The results showed that patients with higher oxygen saturation (SpO2 > 93%) had a significantly higher survival rate (P < 0.001). Long-term hospitalization was significantly associated with a higher mortality rate (P < 0.001). Of all patients, 4,776 received two or more doses of the vaccine. The results indicated that receiving two or more doses of the vaccine significantly reduced the mortality rate associated with the Omicron variant (P = 0.002). The presence of comorbidities such as diabetes and hypertension significantly increased the mortality rate (P = 0.048). Conclusions: This study investigated the connections between COVID-19 vaccination, patient demographics, comorbidities, and hospitalization outcomes. It found that mortality risk was influenced by age, blood oxygen levels (SpO2), and booster doses, while longer hospital stays and certain comorbidities increased the risk. This highlights the need for ongoing research and standardized vaccine categorization to manage the pandemic effectively.