Differences in the severity and mortality risk factors for patients hospitalized for COVID-19 pneumonia between the early wave and the very late stage of the pandemic

Differences in the severity and mortality risk factors for patients hospitalized for COVID-19 pneumonia between the early wave and the very late stage of the pandemic
Li et al., Frontiers in Medicine, doi:10.3389/fmed.2023.1238713
https://c19early.org/li25.html