Abstract
Objectives: This study aimed to assess the effectiveness of the COVID-19 vaccine on the outcomes of patients in three hospitals in Vietnam. Methods: An observational study involved 3102 confirmed COVID-19 patients from Vietnam. Participants were classified into unvaccinated, partially vaccinated (one dose) (PV), fully vaccinated (two doses) (FV), and boosted (three doses) groups. We used a regression model to assess the relationship between vaccine status and disease outcome, including mortality, persistent symptoms after treatment, and hospital duration. Results: The proportions of unvaccinated, PV, FV, and boosted groups were 43.39%, 4.63%, 43.93%, and 8.05%, respectively, and 48% of the participants had at least one comorbidity. The proportion of severe clinical disease was significantly higher in the unvaccinated compared with the vaccinated. Biomarkers of cellular injury and organ failure, e.g., aspartate aminotransferase (AST), ferritin, troponin T, proBNP, D-dimer, and urea plasma concentration were significantly higher in unvaccinated and PV patients compared with FV and boosted patients. Age was the most crucial predictor of critical illness, followed by vaccine status, hypertension, diabetes, heart disease, and chronic kidney disease. The unvaccinated group had the highest proportion of deaths (5.2% vs. 1.4% and 0.3% in FV and boosted groups, respectively). Conclusions: Vaccination reduced mortality and both hospitalization length and disease severity in COVID-19 survivors, especially the older and patients with chronic comorbidities.