HLA-DRB1 and COVID-19: Furthermore, the frequency of HLA-DRB1*04:01 was higher in asymptomatic individuals, suggesting its association with resistance; and the frequency of the haplotype DQA1*01:01-DQB1*05:01-DRB1*01:01 was lower in the asymptomatic group, suggesting its correlation to COVID-19 severity55.