Two studies suggest people with blood type O may have a lower risk of COVID-19 infection and reduced likelihood of severe outcomes, including organ complications, if they do get sick. As the pandemic continues, the global biomedical research community is working urgently to identify coronavirus risk factors and potential therapeutic targets. The potential role of blood type in predicting risk and complications of COVID-19 infection has emerged as an important scientific question. These new studies add evidence that there may be an association between blood type and vulnerability to COVID-19; however, additional research is needed to better understand why and what it means for patients.
Blood type O may offer some protection against COVID-19 infection, according to a retrospective study . Researchers compared Danish Health Registry data from more than 473,000 individuals tested for COVID-19 to data from a control group of more than 2.2m people from the general population. Among the COVID-19 positive, they found fewer people with blood type O and more people with A, B, and AB types.
The study results suggest that people with blood types A, B, or AB may be more likely to be infected with COVID-19 than people with type O. The researchers did not find any significant difference in rate of infection between A, B, and AB types. Since blood group distributions vary among ethnic subgroups, the researchers also controlled for ethnicity and maintained that fewer people with blood type O tested positive for the virus.
"It is very important to consider the proper control group because blood type prevalence may vary considerably in different ethnic groups and different countries," said study author Dr Torben Barington, of Odense University Hospital and the University of Southern Denmark. "We have the advantage of a strong control group – Denmark is a small, ethnically homogenous country with a public health system and a central registry for lab data – so our control is population-based, giving our findings a strong foundation."
Blood groups A and AB associated with increased risk of severe clinical outcomes of COVID-19 infection
People with blood groups A or AB appear to exhibit greater COVID-19 disease severity than people with blood groups O or B, according to a separate retrospective study. Researchers examined data from 95 critically ill COVID-19 patients hospitalised in Vancouver, Canada. They found that patients with blood groups A or AB were more likely to require mechanical ventilation, suggesting that they had greater rates of lung injury from COVID-19. They also found more patients with blood group A and AB required dialysis for kidney failure.
Together, these findings suggest that patients in these two blood groups may have an increased risk of organ dysfunction or failure due to COVID-19 than people with blood types O or B. Furthermore, while people with blood types A and AB did not have longer overall hospital stays than those with types O or B, they did remain in the intensive care unit (ICU) for a longer average time, which may also signal a greater COVID-19 severity level.
"The unique part of our study is our focus on the severity effect of blood type on COVID-19. We observed this lung and kidney damage, and in future studies, we will want to tease out the effect of blood group and COVID-19 on other vital organs," said study author Dr Mypinder S Sekhon, of the University of British Columbia. "Of particular importance as we continue to traverse the pandemic, we now have a wide range of survivors who are exiting the acute part of COVID-19, but we need to explore mechanisms by which to risk stratify those with longer-term effects."
Abstract 1
Identification of risk factors for contracting and developing serious illness following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of paramount interest. Here, we performed a retrospective cohort analysis of all Danish individuals tested for SARS-CoV-2 between 27 February 2020 and 30 July 2020, with a known ABO and RhD blood group, to determine the influence of common blood groups on virus susceptibility. Distribution of blood groups was compared with data from nontested individuals. Participants (29% of whom were male) included 473 654 individuals tested for SARS-CoV-2 using real-time polymerase chain reaction (7422 positive and 466 232 negative) and 2 204 742 nontested individuals, accounting for ∼38% of the total Danish population. Hospitalization and death from COVID-19, age, cardiovascular comorbidities, and job status were also collected for confirmed infected cases. ABO blood groups varied significantly between patients and the reference group, with only 38.41% (95% confidence interval [CI], 37.30-39.50) of the patients belonging to blood group O compared with 41.70% (95% CI, 41.60-41.80) in the controls, corresponding to a relative risk of 0.87 (95% CI, 0.83-0.91) for acquiring COVID-19. This study identifies ABO blood group as a risk factor for SARS-CoV-2 infection but not for hospitalization or death from COVID-19.
Authors
Mike Bogetofte Barnkob, Anton Pottegård, Henrik Støvring, Thure Mors Haunstrup, Keld Homburg, Rune Larsen, Morten Bagge Hansen, Kjell Titlestad, Bitten Aagaard, Bjarne Kuno Møller, Torben Barington
Abstract 2
Studies on severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) suggest a protective effect of anti-A antibodies against viral cell entry that may hold relevance for SARS-CoV-2 infection. Therefore, we aimed to determine whether ABO blood groups are associated with different severities of COVID-19. We conducted a multicenter retrospective analysis and nested prospective observational substudy of critically ill patients with COVID-19. We collected data pertaining to age, sex, comorbidities, dates of symptom onset, hospital admission, intensive care unit (ICU) admission, mechanical ventilation, continuous renal replacement therapy (CRRT), standard laboratory parameters, and serum inflammatory cytokines. National (N = 398 671; P = .38) and provincial (n = 62 246; P = .60) ABO blood group distributions did not differ from our cohort (n = 95). A higher proportion of COVID-19 patients with blood group A or AB required mechanical ventilation (P = .02) and CRRT (P = .004) and had a longer ICU stay (P = .03) compared with patients with blood group O or B. Blood group A or AB also had an increased probability of requiring mechanical ventilation and CRRT after adjusting for age, sex, and presence of ≥1 comorbidity. Inflammatory cytokines did not differ between patients with blood group A or AB (n = 11) vs O or B (n = 14; P > .10 for all cytokines). Collectively, our data indicate that critically ill COVID-19 patients with blood group A or AB are at increased risk for requiring mechanical ventilation, CRRT, and prolonged ICU admission compared with patients with blood group O or B. Further work is needed to understand the underlying mechanisms.
Authors
Ryan L Hoiland, Nicholas A Fergusson, Anish R Mitra, Donald EG Griesdale, Dana V Devine, Sophie Stukas, Jennifer Cooper, Sonny Thiara, Denise Foster, Luke YC Chen, Agnes YY Lee, Edward M Conway, Cheryl L Wellington, Mypinder S Sekhon
[link url="https://www.hematology.org/newsroom/press-releases/2020/possible-link-between-blood-type-and-covid-19"]American Society of Hematology material[/link]
[link url="https://ashpublications.org/bloodadvances/article/4/20/4990/463793/Reduced-prevalence-of-SARS-CoV-2-infection-in-ABO"]Blood Advances 1 full study[/link]
[link url="https://ashpublications.org/bloodadvances/article/4/20/4981/464437/The-association-of-ABO-blood-group-with-indices-of"]Blood Advances 2 full study[/link]