Comparison of COVID-19 Severity in Vaccinated and Unvaccinated Patients during the Delta and Omicron Wave of the Pandemic in a Romanian Tertiary Infectious Diseases Hospital

Abstract

Romania has a poor uptake of COVID-19 vaccination in its population. The study objectives were to evaluate the differences between vaccinated and unvaccinated hospitalized COVID-19 patients with regard to disease severity, intensive care need, and mortality during the fourth and the fifth wave of the pandemic associated with the Delta and Omicron variants of concern. A retrospective study on a cohort of hospitalized COVID-19 patients was performed in a Romanian tertiary hospital for infectious diseases. Multivariate logistic regression models were built predicting severe/critical COVID-19, intensive care need, and death as a function of vaccination status and adjusted for age, comorbidities, and wave of the pandemic. 2235 COVID-19 patients were included, and vaccination status, as a primary vaccination or a booster dose, was described in 750 (33.5%). Unvaccinated patients were older, with more cardiovascular and endocrine diseases, a longer duration of hospitalization, a higher percentage of severe/critical COVID-19, need for intensive care, and death (p < 0.05). The multivariate logistic regression models adjusted for age and comorbidities showed higher odds ratio for severe/critical COVID-19, intensive care need, and mortality in unvaccinated versus vaccinated patients. Our results support vaccination to prevent severe outcomes associated with COVID-19 due to both variants of concern.

Keywords: COVID-19; comorbidities; disease severity; mortality; vaccination.

Figure 1

Duration of hospitalization in the three subgroups of patients (unvaccinated/incomplete vaccinated, complete primary vaccination, and booster) during the fourth and the fifth wave of the pandemic. Box represents median observations (horizontal rule) with 25th and 75th percentiles of observed data (top and bottom of box). The length of each whisker represents values up to 1.5 times the interquartile range.

Figure 2

Time interval represented in months between the date of last vaccine administered (primary vaccination or booster vaccination) and hospitalization date.