Effect of vaccination on the severe forms of COVID-19 disease: results from the hospitalized cohort in Sahloul University Hospital-Tunisia

Context: Coronavirus disease registered a high morbidity and mortality. Tunisia was one of the most affected nations until vaccination became a potential resolution of the threat. <bold>Aim:</bold> Our study aimed to determine the effect of COVID-19 vaccination on the disease severity. <bold>Methods:</bold> A longitudinal study was conducted among confirmed COVID -19 vaccinated patients hospitalized in Sahloul University Hospital since the beginning of vaccination campaigns until September 2022. We compared severity , including length of stay, need for intensive care unit (ICU), need for mechanical ventilation(intubation) and mortality. A univariate analysis of each one of these severity criteria was performed. Independent risk factors associated with COVID-19 vaccination were determined using a multilevel regression. <bold>Results:</bold> Our study included 411 patients, 57.2% were vaccinated. Vaccinated patients from those who had comorbidities were significantly more than those without comorbidities (81.3%VS67.0%;p=0.001) especially those with cardiac diseases (27.7%VS 15.9%,p=0.005). However, the percentage of vaccinated patients suffering from obesity was less important than that of unvaccinated patients (2.1% VS 6.3%; p=0.033). There was no significant difference in ‘intubation’ or ICU hospitalization between those who received and did not receive an influenza vaccination (p=0.297 and p=0.193, respectively). However, mortality and the mean length of stay were significantly more important within unvaccinated patients (p=0.039, p=0.002). <bold>Conclusion:</bold> Our study highlighted the critical role of vaccination in reducing COVID-19 severity.