Does my blood type put me vulnerable to getting Covid-19?

Stay positive! This is my motto and my blood type. But is it a hidden risk factor for coronavirus disease 2019 (COVID-19)? Recent reports have confirmed the hypothesis that blood type is related to Covid-19. Should we be concerned about these recent discoveries?

COVID-19 and blood type: a fast overview

First, let us take a look at the fundamentals about blood type. Your blood type is decided by the presence or absence of specific antigens (A and B) on the surface of red blood cells and antibodies (A and B) within the plasma (American Red Cross, 2020). In addition to the A and B antigens and antibodies, there may be a protein called Rh factor, which could also be present (+) or absent (-). The combination of those ingredients produces eight common blood types: A+, A-, B+, B-, O+, O-, AB+, AB-. For nurses, knowing a patient’s blood type is crucial when administering blood products to stop fatal transfusion reactions.

*Source: WebMd, 2020

Is blood type linked to Covid-19?

Studies conducted on the primary severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1) have shown that anti-A antibodies in individuals with blood groups O or B can block the interaction between the virus and the angiotensin-converting enzyme 2 (ACE2) receptor found on cells, which is the mechanism of virus transmission (Guillon et al., 2008). SARS-CoV-2 also binds to ACE2 and subsequently anti-A antibodies might also affect it. Additional studies have shown that patients with blood group O have reduced levels of factor VIII and von Willebrand factor, potential aspects which will provide a protective effect against pulmonary vascular abnormalities (Hoiland et al., 2020).

A study conducted within the early days of the SARS-CoV-2 pandemic by Zhao et al. (2020) examined 2,173 patients and located that ABO blood type is a biomarker of susceptibility to Covid-19. Their study found that folks with blood type A were at higher risk of Covid-19, and blood type O was related to a lower risk of infection in comparison with non-O blood types. This study had several limitations, corresponding to a small sample size, and the control population didn’t have information on the age, gender and chronic diseases of the participants, which made it not possible to conduct a correct evaluation making an allowance for these aspects.

This month (October 2020), the journal published two recent studies on Covid and blood type, supporting the speculation that folks with blood type O are less prone to contract Covid-19 and severe coronavirus disease.

The first study by Hoiland et al. (2020) assessed whether ABO blood groups are related to different degrees of COVID-19 severity. This was a multicenter, retrospective evaluation and prospective observational study of patients requiring intensive care (n = 95). Their study found that a greater proportion of Covid-19 patients with blood type A or AB required mechanical ventilation and continuous renal alternative therapy (CRRT) and stayed within the intensive care unit (ICU) (13.5 days) in comparison with patients with blood type O or B. Biomarkers of renal (serum creatinine) and liver dysfunction (AST, ALT) were higher in patients with blood type A or AB. These results indicate severe lung damage, in addition to worsening kidney and liver disease. Inflammatory cytokine levels didn’t differ between patients with blood type A or AB compared with type O or B, and the entire length of hospital stay didn’t differ between groups. This study has several limitations. First, in a retrospective evaluation of observational data, researchers were unable to prove a causal relationship. Second, the sample size was small and lacked statistical power. Additionally, the titer of anti-A antibodies may influence the severity of the Covid-19 virus, and these levels weren’t analyzed but inferred from blood type data.

A second study conducted in Denmark by Barnkob et al. (2020) is a big retrospective cohort evaluation that aimed to find out the impact of typical blood types on virus susceptibility. The evaluation compared greater than 473,000 individuals with Covid-19 with greater than 2.2 million people in the final population. Of those testing positive for Covid-19, significantly fewer people were detected with blood type O in comparison with the next proportion of individuals with blood types A, B and AB. There was no difference between ABO blood types and clinical severity of COVID-19 in nonhospitalized patients compared with hospitalized patients or for deceased patients compared with living patients. The researchers concluded that blood type O is related to reduced susceptibility to SARS-CoV-2 infection in comparison with blood types A, B and AB. However, ABO blood types didn’t correlate with the speed of hospitalization or death following infection.

How does COVID and blood type research impact clinical practice?

Although preliminary research suggests a robust link, we don’t yet understand how this can impact clinical practice. Further research is required to find out whether ABO blood type testing ought to be used to treat SARS-CoV-2 infection and whether COVID-19 patients with non-O blood type require more aggressive treatment. Until more data is collected, physicians should proceed to follow current protocols within the care of Covid-19 patients. Additionally, the general public must remain vigilant regarding the duty to wear masks, maintain physical distancing and practice strict hand hygiene.

COVID and blood type references

American Red Cross (2020). Facts about blood and blood types. Downloaded from https://www.redcrossblood.org/donate-blood/blood-types.html

Barnkob, M. B., Pottegard, A., Stovring, H., Haunstrup, T. M., Homburg, K., Larsen, R., Hansen, M. B., Tiltlestad, K., Aagaard, B. Moller, B. K., and Barinton, T. ( 2020). Reduced incidence of SARS-CoV-2 infection in ABO O blood group. 4(20), 4990 – 4993. DOI: 10.1182/bloodadvances.2020002657

Guillon, P., Clement, M., Sebille, V., Rivain, J., Chou, C., Ruvoen-Clouet, N., Le Pendu, J. (2008). Inhibition of the interaction between SARS-CoV spike protection and its cellular receptor by anti-histogroup antibodies. Glycobiologia. 18(12), 1085-1093. doi: 10.1093/glikob/

Hoiland, R.L., Fergusson, N.A., Mitra, A.R., Griesdale, D.E.G., Devine, D.V., Stukas, S., Cooper, J., Thiara, S., Foster, D., Chen, L.Y.C., Lee, A.Y.Y., Conway, E. M., Wellington, C. L., Sekhon, M. S. (2020). Association of ABO blood group with indicators of disease severity and multi-organ dysfunction in the midst of COVID-19. Blood progress. 4(20), 4981 – 4989. DOI: 10.1182/bloodadvances.2020002623

WebMD. (2020). Blood groups: what’s value knowing – different blood groups. Downloaded from https://www.webmd.com/a-to-z-guides/blood-types-what-to-know#1

Zhao, J., Yang, Y., Huang, H., Li, D., Gu, G., Lu, X., Zhang, Z., Liu, T., Liu, Y., He, Y., Sun, B., Wei, M., Yang, G., Wang, X., Zhang, L., Zhou, X., Xing, M., and Wang, P. G. (2020). Association between ABO blood group and susceptibility to COVID-19. . August 4, 2020 DOI: https://doi.org/10.1101/2020.03.11.20031096