Clinical Profile and Outcome of Vaccinated and Unvaccinated COVID-19 Patients From March 2021 to March 2022

Background: The COVID-19 vaccination significantly reduces the risk of SARS-CoV-2 infection. However, there are still uncertainties about the full protection against emerging variants. Breakthrough infections occur despite full vaccination. Methods: This is a retrospective, cohort study performed at the University of Santo Tomas Hospital, a tertiary teaching hospital in Manila, Philippines. All USTH admitted COVID-19 confirmed patients referred to pulmonary team practice from March 2021 till March 2022 age ≥ 18 y were included. Descriptive statistics were used to summarize the socio-demographic data and vaccination status of the patients. Categorical variables were summarized using frequency and proportion, while non-normally distributed continuous variables were summarized using median and interquartile range, and normally distributed continuous variables were summarized using mean and standard deviation. Chi-square was used to test associations between categorical variables, and the t-test for independent samples was used to determine significant differences. A P -value < .05 was considered statistically significant. Data analysis was performed using SPSS version 23. The Research Ethics Committee (REC) of the USTH reviewed and approved the study protocol (Reference No. REC-2021-10-131-TF). Results: Out of 381 patients, 190 were above age of 65 and the majority were men. The two most common co-morbidities were hypertension and diabetes mellitus. The unvaccinated (53.2%) and partially vaccinated group (68.4%) had the highest incidence of severe COVID-19 cases. Most of the fully vaccinated patients had moderate infections (44.7%; P < .05). Mechanical ventilation (25.4%) and high flow nasal cannula (44.8%) were administered to the unvaccinated group. In contrast, fully vaccinated patients were mostly on high flow nasal cannula (35%) and not receiving oxygen support (32.5%; P < .05). Higher mean average of serum LDH (527.6 ± 394), ferritin (2,300 ± 3,781), C-reactive protein (207.7 ± 480.1), procalcitonin (10.1 ± 45.85), lymphocytes (0.220 ± 0.102), and interleukin-6 (215.6 ± 571.2) were seen among the unvaccinated group. They also had longer hospital stays and a higher mortality incidence (14.089.26, 29.1%). Most patients (72.2%) were discharged improved. Conclusions: Full vaccination status was associated with lower mortality and required less invasive ventilation compared with unvaccinated group.Table 1. Clinico-Demographic Characteristics of COVID 19 Patients, Section of Pulmonary and Critical Care, Department of Internal Medicine - University of Santo Tomas Hospital, Manila, March 2021 to March 2022Table 2.