Comparative admission rates and infection severity of COVID-19 among unvaccinated and vaccinated patients

Vaccination efforts have limited the burden of the pandemic caused by the coronavirus disease 2019 (COVID-19) with substantial evidence showing reduced hospitalization rates among vaccinated populations. However, few studies have explored correlations between vaccination status and inpatient COVID-19 outcomes. This observational case-control study involved a retrospective chart review of adult patients hospitalized for COVID-19 infection at a medium-sized hospital in Central Michigan between May 1, 2021 and September 30, 2021. Unadjusted analyses involved t-tests and chi-square tests followed by adjusted analyses using binary logistic and linear regression models. Of the 192 screened patients, 171 subjects met the inclusion criteria. Vaccinated patients were significantly older (71.09 vs 57.45, p < 0.001), more likely to identify as white (89.4% vs 66.9%, p = 0.026), and had a lower baseline 10-year survival rate predicted by the Charlson Comorbidity Index (42% vs 69%, p < 0.001) compared to unvaccinated patients. Common symptoms between both groups included shortness of breath (50%), malaise (23%-37%), cough (28%-32%), and fever or chills (25%). Upon matching, adjusted analysis showed significantly higher rates of remdesivir administration to unvaccinated patients (41.3% vs 13.3%, odds ratio (OR): 4.63, 90% confidence interval (CI): 1.98-11.31). Despite higher intensive care unit admission rates among unvaccinated patients (39.1% vs 23.9%, OR: 1.83, 90% CI: 0.74-4.64), this difference did not reach statistical significance. Accordingly, immunization status strongly correlates with patient demographics and differences in inpatient treatment. Larger studies are needed to further assess the vaccine's impact on inpatient outcomes outside of our community.