BackgroundSARS-CoV-2 (COVID-19) created unprecedented recurrent waves of pandemic globally. Apart from COVID-19-appropriate behavior, vaccinating the population was proposed to be the most effective measure to control these outbreaks. However, the outcomes of vaccinated patients admitted to the intensive care unit (ICU) and their comparison with unvaccinated counterparts, especially in developing countries, have not been extensively studied.Materials and methodsOur study examined consecutive patients with positive RT-PCR for COVID-19 admitted to the ICU from August 1, 2021, to July 31, 2022. Prior vaccination status and its relation to demographics, disease severity, mortality, and length of stay were analyzed.ResultsAmong 436 patients admitted to the ICU, 76 (15.4%) were unvaccinated and 369 (84.6%) were vaccinated against COVID-19. Vaccinated patients were significantly older and hypertensive, and had comparatively less severity of illness than unvaccinated patients. Crude ICU and hospital mortality were significantly lower among vaccinated patients than unvaccinated patients (15.2% versus 25.4% and 16% versus 22.3%, respectively; P<0.05). Furthermore, risk-adjusted multivariate analysis demonstrated a strong but statistically nonsignificant inverse association between vaccination status and ICU mortality (odds ratio (OR)=0.540, 95% confidence interval (CI)=0.290-1.006, P=0.052).ConclusionIn severe COVID-19-infected patients who required admission to the ICU, the majority were vaccinated. However, the severity of illness and hospital mortality was significantly lower among vaccinated patients with breakthrough infections.