Objective: This retrospective study aimed to examine the outcomes of cohorts of patients who had uncomplicated type II diabetes mellitus as their only documented chronic condition. We compared fully vaccinated and non-vaccinated populations within different sex and age groups, considering their clinical outcomes.Design: From March 2020 to June 2022, an extensive retrospective analysis was carried out using national patient data obtained from the database of the Ministry of Health of the Republic of Bulgaria, following a formal written request. The study encompassed a total of 1,126,946 confirmed COVID-19 patients.Results: Among the 1,126,946 confirmed COVID-19 patients included in this study, 0.33% (n=3,792) had type II diabetes mellitus as their sole chronic condition. Statistical analysis revealed significant findings in favor of the vaccinated cohorts, demonstrating reduced rates of hospitalizations [0.76 (95% CI 0.6550 to 0.9001); p=0.0011], ICU admissions [OR=0.38 (95% CI 0.2698 to 0.5282); p < 0.0001], in-hospital mortality [0.20 (95% CI 0.1126 to 0.3552); p<0.0001], and ICU-related mortality [0.25 (95% CI 0.0789 to 0.7860; p=0.0178]. Furthermore, the vaccinated cohort exhibited lower hospitalization rates specifically during the alpha wave of the pandemic. Statistically significant reductions in mortality rates were observed in the vaccinated cohorts during the beta [OR=0.01 (95% CI 0.0008 to 0.2085); p=0.0022], delta [OR=0.42 (95% CI 0.2636 to 0.6842); p=0.0004], and omicron [OR=0.20 (95% CI 0.1321 to 0.3132); p < 0.0001] waves. Additionally, within the vaccinated cohorts, those who received mRNA-based vaccines experienced higher and more significant reduction rates compared to those who received viral-vector-based vaccines.
Conclusion:This retrospective analysis highlights a consistent pattern among patients with uncomplicated type II diabetes mellitus as the sole chronic condition who have received COVID-19 vaccination. Notably, vaccinated individuals have demonstrated a decrease in both the severity of COVID-19 cases and the rates of premature mortality.