Description of Hospitalizations due to the SARS-CoV-2 Omicron Variant Based on Vaccination Status

Abstract Background Limited descriptive data exist regarding the clinical characteristics of hospitalizations due to the SARS-CoV-2 Omicron variant based on vaccination status. Methods This was a retrospective cohort study of all patients hospitalized with a diagnosis of COVID-19 between 1/15/22-2/15/22 across 9 hospitals in a large health network. Data was extracted by manual chart review. Results A total of 351/452 (77.7%) unvaccinated, 209/331 (63.1%) fully vaccinated, and 107/163 (65.6%) boosted patients hospitalized with a COVID-19 diagnosis were determined to be admitted specifically due to COVID-19 (P < .001). Most (85%) boosted patients admitted due to COVID-19 were at least 65 years old and/or had severe immune suppression, compared to 72.2% of fully vaccinated and 60.7% of unvaccinated patients (P < .001). Significantly more unvaccinated patients (34.2%) required greater than 6 liters/minute of supplemental oxygen compared to fully vaccinated (24.4%) and boosted (25.2%) patients (P = .027). The age-adjusted vaccine effectiveness (VE) against hospitalization due to COVID-19 was estimated to be 81.1% and 94.1% for full vaccination and boosted status, respectively, while VE against mortality related to COVID-19 was estimated to be 84.7% and 94.8%, respectively. Conclusions During the Omicron BA.1 sublineage wave, unvaccinated patients hospitalized with a COVID-19 diagnosis were more likely to be admitted specifically due to COVID-19 compared to vaccinated patients. Despite being younger with fewer comorbidities, unvaccinated patients required higher levels of care. Vaccination with a booster provides the greatest protection against hospitalization and death from COVID-19.