Comparison of fully-vaccinated and non/partially-vaccinated critically-ill COVID-19 patients in terms of disease severity: a retrospective observational study.

BACKGROUND: Critical care admissions due to breakthrough COVID-19 in fully vaccinated patients remain rare. There is limited data on their characteristics and outcomes compared to non- or partially vaccinated patients, and no studies have evaluated the impact of variants of concern. METHOD: This study used the COMETE-19 (COVID-19 patients in the intensive care unit [ICU]) near real-time prospective registry, a tool launched on March 1, 2020, to track patient and disease characteristics as well as the disease course of critically ill COVID-19 patients in two French ICUs. Fully vaccinated patients were compared with non- or partially vaccinated patients. The primary outcome was a composite criterion of severity, including invasive mechanical ventilation (IMV), other organ assistance, or death. Differences between the vaccinated and control groups regarding other outcomes, patient variables, management, and SARS-CoV-2 variants were explored using univariate analysis. Factors associated with high disease severity in both groups were examined using logistic regression analysis. RESULTS: A total of 805 patients (median age, 65 years [IQR 56-71], 67% male) were enrolled. Of these, 41 (5%) were fully vaccinated. Fully vaccinated patients required less frequent IMV (27% vs. 51%, p = 0.003) and had lower mortality (15% vs. 26%, p = 0.026). Full vaccination status was associated with lower disease severity (OR 0.30; CI95% [0.11-0.74]; p = 0.011) and tended to prevent ICU mortality (OR 0.39, CI95% [0.13-1.04], p = 0.072). Variants-of-concern did not associate with outcomes. CONCLUSION: Among critically ill COVID-19 patients, full vaccination was associated with less severe disease progression compared to partial or no vaccination. TRIAL REGISTRATION: Clinical Trial: NCT04430322.