Tehran University of Medical Sciences Journal of Medical Bacteriology 2251-8649 12 2 2024 04 17 26 33 Mohamad Mahjoor epartment of Immunology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran Abolfazl Askari 2. Cellular and Molecular Research Center, Basic Health Sciences Institute, Shahrekord University of Medical Sciences, Shahrekord, Iran Mansoor Khaledi Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran Hamed Afkhami Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran. Hamed Sadeghi-dehsahraei 4. Department of Basic Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran Javad Arabpour 5. Young Researchers and Elite Club, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran. Javad Fathi 7. Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Amir Valizadeh 8. Molecular Medicine Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Mohammad Esmaeil Amini Department of Microbiology, school of Medicine, Guilan University of Medical Science, Rasht, Iran Mohammad Esmkhani 10. Department of Biochemistry, Islamic Azad University, Zanjan University, Zanjan, Iran Reza Safarinia , Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran Zahra Mottaghiyan 3. Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran 2024 01 07 2024 01 09 Background: ABO blood types are not known to cause diseases directly, but they can be vulnerable and surrender to diseases and health problems. This study aimed to evaluate the susceptibility to COVID-19 in individuals with different blood groups at different ages. Methods: An electronic health record was used in this retrospective cohort study at Shahid Beheshti Hospital. We studied 858 patients who were referred to Shahid Beheshti Hospital, we identified 434 of them as COVID-19 patients using RT-PCR. An analysis of the electronic record involved collecting retrospective laboratory data and demographic information, including age, sex, and blood type. Next, we examined the differences between the ABO blood groups of COVID-19 patients and the control group (1991 case). We used SPSS26 for statistical computations. Data were scrutinizeed with the χ2 test. P < 0.05 was considered statistically outstanding. Results: Based on the distribution of ABO blood groups in 434 COVID-19 patients, it was revealed that 288 of them were male and 146 were female, and the majority of them were in their third decade of life. A total of 159 patients (36.6%) had type B blood, 116 had type A (26.7%), 109 had type O (25.1%), and 50 had type AB (11.5%). COVID-19 patients had a higher percentage of type B and AB blood than the control group. Conclusion: Our study found that the frequency ratio of blood group B was remarkably higher in patients than in the control group, which indicates that the blood group B may play a pivotal role in COVID-19  disease. https://jmb.tums.ac.ir/index.php/jmb/article/view/508