Clinical characteristics and severity markers in hospitalized COVID-19 patients from western Mexico: a comparative analysis of Delta and Omicron variants

Patients hospitalized with the Omicron were found to be older, compared to those infected with the Delta (64 vs. 54 years, <i>p</i> = 0.006). Additionally, a higher proportion of male patients were observed in the Omicron compared to the Delta (<i>p</i> = 0.029). Both Omicron and Delta variants were associated with lymphopenia, although the lymphocyte count was lower in Omicron (0.9 vs. 0.56 10x³/L; <i>p</i> = 0.007). The COVID-GRAM scale indicated a high risk for severe disease in both groups, but the score was higher in Omicron compared to Delta (157 vs. 128 points; <i>p</i> = 0.0004). Patients infected with Omicron exhibited a lower percentage of neutralizing antibodies than those with Delta (35.99 vs. 81%; <i>p</i> < 0.05), regardless of their vaccination status. Among the markers assessed, globular ESR was found to be lower in Omicron compared to Delta (30.5 vs. 41.5 mm/h; <i>p</i> = 0.001), while ferritin levels were higher in patients infected with the Omicron (1,359 vs. 960.6 μg/L; <i>p</i> = 0.007). In patients with severe COVID-19, markers such as lymphopenia, neutralizing antibody levels, ferritin, and COVID-GRAM scores are elevated in the Omicron variant, while only the leukocyte count and ESR for the Delta variant.