HLA-DRB1 and COVID-19: Instead, another study performed on a cohort of COVID-19 patients with severe (respiratory impairment, requiring non-invasive ventilation) and extremely severe (respiratory failure, requiring invasive ventilation and ICU admission) disease showed that the frequency of HLA-B*27:07, -DRB1*15:01, -DQB1*06:02 was higher in the studied COVID-19 patients vs. a reference group representing the local Italian population (Table 2) [41].