Hospitalization Outcomes of Coronavirus Disease 2019 (COVID-19) Patients by Vaccination Status: A Population-Based Study in Dezful, Iran

Background: Coronavirus disease 2019 (COVID-19) vaccines have been crucial in decreasing disease severity, hospitalization, and mortality globally. However, the effectiveness of these vaccines can differ based on vaccine type, dosage, and patient characteristics. Objectives: This study evaluates the impact of immunization status on hospitalization outcomes among COVID-19 patients in Dezful, southwest Iran. Methods: This population-based cross-sectional study examined 5,600 patients with PCR-confirmed COVID-19 from June to September 2021. Data were gathered from hospital and public health databases. Patients were divided into outpatient and hospitalized groups. We analyzed immunization status, the number of doses (0 - 3), and vaccine type concerning clinical outcomes. Statistical analyses included chi-square tests and t-tests, with significance set at P < 0.05. Results: Of the 5,600 patients, 4,906 (87.61%) were outpatients, while 694 (12.39%) were hospitalized. A total of 655 patients (11.70%) died. Hospitalization was significantly higher among unvaccinated individuals (89.81%) compared to those who received three doses (61.40%, P < 0.001). The risk of hospitalization was also significantly lower for individuals who received the first (P < 0.001), second (P < 0.001), or third (P = 0.002) vaccine dose. Additionally, the type of vaccine impacted outcomes: Patients vaccinated with Sputnik V or AstraZeneca had lower hospitalization rates compared to those who received Sinopharm (P < 0.001). Among the deceased, 81.53% were unvaccinated, and only 0.76% had received a third dose. Conclusions: This study demonstrates that COVID-19 immunization significantly lowers hospitalization and mortality rates. Receiving higher doses correlates with improved outcomes, highlighting the importance of full immunization and booster shots. These results reinforce public health initiatives aimed at increasing vaccine coverage, particularly among high-risk populations.