An outlook on clinical and demographic variables in patients with severe COVID-19 across different waves in Mexico and SARS-CoV-2 variants: data from two high-specialty centers

Background Throughout the COVID-19 pandemic, there was variability in outcomes and in the clinical and demographic characteristics of patients with severe disease. We aimed to compare clinical and demographic variables at hospital admission among patients with severe COVID-19 at two high-specialty centers in Mexico during the pandemic waves, accounting for relevant virus variants and patients' vaccination status. Methods This retrospective, descriptive study included medical records of 1,425 patients hospitalized with COVID-19 (March 2020–November 2022) at the National Institute of Respiratory Diseases (INER, Mexico City, Mexico) and the Regional High Specialty Hospital of the Yucatán Peninsula–IMSS Bienestar (Merida, Yucatán, Mexico). The comparison was performed between the 1st wave, the 2nd and 3rd waves, and the 4th to 6th waves in Mexico, among the pre-dominant SARS-CoV-2 variants (Delta and Omicron), and vaccination status during the Omicron stage. Results At the 1st wave, patients were pre-dominantly male and younger; whereas in the 4th to 6th waves, a high frequency of subjects with heart disease was observed. The longest hospital stay (median 23 days) and the highest percentage of invasive mechanical ventilation (81.02%) were observed during the 2nd and 3rd waves. Heart diseases and D-dimer were relevant during the Omicron stage. Clinical and demographic variables were similar between unvaccinated and vaccinated subjects, although the mortality was lower in the vaccinated group. Conclusions These differences in the studied variables across pandemic waves and SARS-CoV-2 variants help explain the variability in clinical outcomes throughout the COVID-19 pandemic.