Background: The main objective of the present study was to analyze both clinical characteristics and evolution during hospitalization of a cohort of patients admitted for COVID-19 pneumonia who were not vaccinated, or with a complete or incomplete vaccination schedule.
Methods: This COVID-19 specialized single-center cohort study of 1888 COVID-19 patients hospitalized at the "Enfermera Isabel Zendal" Emergencies Hospital (HEEIZ), Madrid (Spain) was performed between July 1 and September 30, 2021. It compared the results of 1327 hospitalized unvaccinated patients to 209 hospitalized fully vaccinated and 352 hospitalized partially vaccinated patients.