INTRODUCTION: An overall milder disease and lower mortality is reported in the Omicron SARS-CoV-2 variant (OV). Since vaccination, outcomes due to severe COVID-19 have changed. Outcomes in Hispanic population have consistently showed higher mortality, however data during Omicron wave (OW) in Mexico is lacking.

AIMS AND OBJECTIVES: To identify the relation of vaccination status with outcomes among Mexican patients hospitalized with severe COVID-19 during the OW.

METHODS: We prospectively collected data from all admitted patients with severe COVID-19 where the OV represented more than 75% of the sequenced samples. Comparisons were made according to survival status. A multivariate logistic regression analysis was performed to identify factors related with mortality.

RESULTS: 118 patients were included, 54% were male, median age of 63 years (IQR 27), 86% of patients with self-reported morbidities (hypertension 40%) and 42% died. 53% of non-survivors had <1 vaccine dose. On admission, non-survivors showed lower SpO2/FiO2 ratio (184 vs 375, p=0.004) and higher qSOFA (2 vs 1, p=0.01), Neutrophil-to-lymphocyte ratio (12 vs 9, p=0.01), C-reactive protein (148 vs 83, p=0.009), and D-dimer (2546 vs 1640, p=0.004). The need of mechanical ventilation (OR 33.3, 95% CI 8.4-127.8, p<0.000) and vaccination with >2 doses (OR 0.32, 95% CI 0.13-0.83, p=0.019) were the main risk factors for mortality during OW.

CONCLUSIONS: In Mexican patients hospitalized with severe COVID-19 during the OW, vaccination (>2 doses) reduced 68% the risk of death. Other routine biomarkers showed a significant association with mortality as has been reported in previous waves.