Clinical Outcomes in Vaccinated and Unvaccinated COVID-19 Inpatient Admissions March to September 2021: A Single Center Retrospective Cohort Analysis (Preprint)

BACKGROUND Background: COVID-19 is an international public health emergency. In the United States, vaccination rates remain modest. Vaccine-mediated immunity is unlikely in the face of emerging variants and surging cases in vaccinated patients give pause to consider the underlying cause. OBJECTIVE To shed light on how COVID effects the public health, especially in an underserved community. Despite development of promising vaccines, surges in COVID cases gives pause to consider affects on age, gender, comorbidities, length of stay, intensive care unit admission, mechanical ventilation, as well as waning immunity METHODS Methods: Retrospective cohort analysis of Emanate Health hospital system from March - September 2021. Demographic and clinical factors for adult inpatient COVID-19 admissions were analyzed using Meditech software. These included age, gender, comorbidities, date of admission, and immunization status. Immunization status was confirmed via the California Immunization Registry. RESULTS Results: Of 475 COVID+ admissions, 28% were vaccinated. Admissions decreased from March to June, but steeply increased from June to August, driven predominately by unvaccinated patients. Length of stay (LOS) was higher for patients 60-79 years and with four and six comorbidities. Mortality was 1.5 times higher in patients 60-79 years and 1.3 times higher in patients with four and six comorbidities. Incompletely vaccinated patients were more likely to require ICU admission and ventilation, causing increased mortality. CONCLUSIONS Conclusions: Poor outcomes in unvaccinated, older patients and those with comorbidities corroborate national data. Among fully vaccinated, LOS did not vary significantly by vaccine type. Mortality increased with age, peaking at 60-79 years. Hypertension, diabetes mellitus, and obesity conferred higher admission and mortality in vaccinated patients, elaborating foci for risk assessment. Our data builds on existing research, demonstrating the protective effects of vaccination, which may decrease vaccine hesitancy. Administration of a booster may be needed earlier than previous federal guidelines recommended to combat waning immunity.