Clinical Characteristics of Vaccinated and Unvaccinated Patients Who Died from COVID-19: A Retrospective Comparative Study

Background: Fatal COVID-19 cases continued to occur after the introduction of vaccination, particularly among older adults and individuals with chronic comorbidities. This study aimed to describe and compare the demographic and clinical characteristics of vaccinated and unvaccinated adults who died from COVID-19. Methods: This single-center retrospective comparative study included 1525 adults who died from RT-PCR-confirmed COVID-19 during hospitalization between January 2021 and June 2022. Patients were classified according to documented prior vaccination status. Demographic characteristics, comorbidities, vaccine dose number, and vaccination regimens were evaluated. Multivariable logistic regression was used to examine associations between demographic and clinical characteristics and prior vaccination status within this fatal-case population. Results: Of 1525 patients, 364 (23.9%) had documented prior vaccination and 1161 (76.1%) were unvaccinated. Patients with prior vaccination were older than unvaccinated patients (median age, 77 vs. 70 years; p < 0.001) and more frequently had at least one comorbidity (84.1% vs. 66.2%; p < 0.001). In multivariable analysis, older age, hypertension, heart failure, COPD/asthma, and malignancy were independently associated with prior vaccination status. Coronary artery disease showed a borderline association (OR, 1.330; 95% CI, 0.997–1.775; p = 0.052). The model showed modest discrimination (AUC = 0.662) and limited explained variance (Nagelkerke R2 = 0.089). Conclusions: Among patients who died from COVID-19, those with documented prior vaccination were older and had a greater burden of several comorbidities than unvaccinated decedents. Because this case-only analysis was restricted to fatal cases and lacked surviving comparison groups and population denominators, the observed associations should be interpreted as descriptive characteristics of the study population and not as estimates of mortality risk or vaccine effectiveness. Differences between vaccination groups may also reflect vaccination prioritization and selection processes inherent in conditioning the analysis on death.