Background: As a new emerging pandemic, COVID-19 is a challenge facing the world. Researches are active to discover factors related to disease severity, as an effort to decrease its impact on health status and mortality.

Aim of the work: The current research aimed at exploring if a relationship is present between ABO blood grouping and disease severity and associated mortality associated with COVID-19.

Patients and Methods: This cross-sectional trial was completed at Al-Azhar University Hospital [New Damietta] between January 2021 to June 2021. It included 100 patients with suspicious clinical manifestations of COVID-19, confirmed by positive reverse transcription real-time polymerase chain reaction (rt RT-PCR) test of swabs obtained from their respiratory tract. All patients were subjected to full medical history taking, thorough clinical assessment, laboratory examinations, chest radiography and high-resolution computerized tomography on chest.

Results: The commonest blood group among the study population was group A in (53%), followed by group O in (19%), then group B in (18%) and group AB in (10%). Individuals with blood group A are significantly susceptible to catch COVID-19 infection (p-value= 0.01), whereas those with blood group O are significantly unsusceptible to be infected (p-value= 0.035). Hypertension was frequent among patients with groups A and B compared with groups AB and O (52.8%, 50.0% versus 20% and 5.2% respectively). There was a significant association between group AB and disease severity (p-value= 0.002), while group A was significantly linked to critical disease and mortality (p-value= 0.032). The vast majority of group O patients (84.2%) had mild disease, whilst mortality was confined to the blood group A.

Conclusion: There is an association between ABO blood groups and either COVID-19 susceptibility, severity and mortality.