Association between mRNA vaccination and COVID-19 hospitalization and disease severity

Introduction: A full understanding of the benefits of vaccination against COVID-19 requires consideration of disease severity, which is defined as whether COVID-19 patients despite vaccination have lower disease severity than unvaccinated individuals. Our udy aims to compare the characteristics and disease progression between vaccinated and unvaccinated severe COVID-19 patients.

Methods: We prospectively reviewed all patients with COVID-19 admitted to a tertiary hospital Pulmonology department between February 25, 2021 and January 20, 2023. Univariate and multivariate analyzes of vaccination-related variables were performed.

Results: Of the 901 hospitalized patients with COVID-19 disease, 351 were vaccinated (39%). They were significantly older and more often with  comorbidities (p<0.001), including ischemic heart disease (p<0.001), COPD (p= 0.001), immunodeficiency (p<0.001) and kidney disease (p<0.002). The radiological extent of the disease was significantly smaller in the vaccinated group(p<0,001). Time from first symptom to hospital admission was longer among unvaccinated patients (5.4 ± 4 days vs. 3 ± 3.5, p < 0.001). Critical illness (p<0.001) and ICU admission (p = 0.002) were less likely in vaccinated. However, mortality (5.7% vs 5.1%, p = 0.68) and length of hospital stay (12.24 ± 7.8 vs 13.4 ± 9.2, p = 0.089) were similar between groups.

Conclusion: Hospitalized vaccinated patients with COVID-19 pneumonia had significantly higher rates of the most known risk factors for adverse outcomes of COVID-19, but disease course and mortality were similar compared to unvaccinated patients.