The Impact of Vaccination Against SARS-CoV-2 Virus on the Outcome of COVID-19 Disease

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a rapidly spreading infection that is on the rise. New variants are continuously appearing with variable degrees of lethality and infectivity. The extensive work since the start of the pandemic has led to the evolution of COVID-19 vaccines with varying mechanisms. We aim to determine real-world data by looking at the different clinical outcomes associated with COVID-19 vaccination, focusing on the rate of hospitalization, severity, and mortality. METHODOLOGY: A retrospective observational study included 624 patients with COVID-19 infection who were hospitalized at King Fahad Hospital of the University and King Fahad Military Medical City between April and July 2021. The cohort was divided into 3 groups: unvaccinated, partially vaccinated (PV), and fully vaccinated (FV). The severity and outcome of COVID-19 disease were compared among the three groups. Among the vaccinated group, we studied the effect of vaccine type on the severity and outcome of COVID-19 disease. RESULTS: We found that 70.4% of patients with COVID-19 disease who required hospitalization were unvaccinated. Un-vaccination was a significant predictor of critical COVID-19 disease (OR 2.31; P <0.001), whereas full vaccination was associated with significantly milder disease severity (OR 0.36; P 0.01). Moreover, un-vaccination status was an independent predictor of longer hospitalization (OR 3.0; P <0.001), a higher requirement for ICU admission (OR 4.7; P <0.001), mechanical ventilation (OR 3.6; P <0.001), and death (OR 4.8; P <0.001), whereas the FV group had a lower risk of ICU admission (OR 0.49; P 0.045). Unvaccinated patients with comorbidities had worse severity and outcome of COVID-19 infection (P<0.05). Both vaccine types (Pfizer and AstraZeneca) had similar protective effects against the worst outcomes of COVID-19 disease. CONCLUSION: COVID-19 vaccination has been shown to be effective in reducing hospitalization, the severity of COVID-19 infection, and improving outcomes, especially in high-risk group patients. COVID-19 vaccination programs should continue to improve the outcome of such a disease.