It’s in the Blood: Unmasking the COVID-19 Blood Type Conundrum
How science is chasing the missing link between blood type and COVID-19 susceptibility and severity
In the early stages of the COVID-19 outbreak, doctors noticed a pattern of infection: an elevated percentage of severe disease patients had type A blood.
Preliminary findings in China
In March 2020, a preliminary study showed that people with type A blood could be more vulnerable to being infected with coronavirus than other blood types. Researchers at Zhongnan Hospital of Wuhan University examined blood group patterns of 2,173 people diagnosed with COVID-19.
The research, conducted from statistics of admissions of patients with the disease, was published on the scientific platform MedRxiv. Back then, the research still needed to be peer-reviewed. Although the researchers acknowledged that their findings were preliminary and required more in-depth studies, they urged governments and medical authorities to consider the different blood types when treating infected patients. Experts pointed out that more in-depth studies were required to substantiate the preliminary findings.
The Chinese researchers found that patients with type A blood had a “significantly higher” infection rate and appeared to develop more severe symptoms of the virus. Of all the blood types, type O seemed to have the lowest risk of infection. According to the study, 85 of the 206 patients who died from covid-19 in Wuhan had type A blood, a rate 63 percent higher than type O.
The research found the same pattern in different age and gender groups. Thus, the study suggested that the higher susceptibility of people with type A blood could be linked to the presence of natural antibodies in the blood. Still, back then, more studies were needed to prove this association.
As a result of the research, the experts suggested that it could be useful to adopt ABO blood type mapping in patients and medical teams as a routine part of managing SARS-CoV-2 and other coronavirus infections. These best practices could help define management options and assess people’s levels of risk exposure.
Follow-up research in Germany
Later on, at the end of the second wave of the pandemic, in June 2020, an analysis of the genome of more than 1,600 severely ill COVID-19 patients and 2,205 healthy people from Italy and Spain found blood type can determine the severity of the disease. The researchers discovered that those with a gene variant that codes for blood type A were 50 percent more likely to have the disease's necessary form and need oxygen support.
German researchers from the University of Kiel followed up on the research mentioned above, trying to identify DNA traits in the human genome that could predispose people to complications caused by the new coronavirus. The results confirmed the preliminary findings, but researchers still couldn’t explain why this genetic variant that leads to type A blood makes someone more susceptible to coronavirus. But, they suspected it could be related to the immune system.
I have debated a similar correlation in this article regarding the impact of BCG vaccination in preventing severe cases of COVID-19. When faced with a threat such as an infection, an overreaction of the immune system can occur, causing a so-called “cytokine storm.” This uncontrolled reaction is one of the main reasons why severe disease patients require advanced life support.
However, the blood type conundrum lingered on, as they couldn’t trace back the connection, and again the enigma remained unclear to the researchers, who also asked for further research on this topic.
Inputs from Denmark and Canada
The findings of two articles, published on October 14 by the scientific journal Blood Advances, confirmed the hypotheses presented earlier. More evidence arose stating how blood type can increase a person’s risk for COVID-19 and severe illness from the disease. The findings showed how individuals from group O tend to be at lower risk, while others are potentially more exposed to severe clinical scenarios.
Scientists from the University Hospital of Odense, Denmark, conducted a retrospective study comparing the health records of more than 473,000 individual covid-19 tests with a control group of 2.2 million from the general population. Those with blood type O were about 13 percent less likely to test positive for covid-19 than those with blood type A, B, or AB. These results, however, did not imply a higher risk of hospitalization, the Danish authors emphasize.
In the second study, from the University of British Columbia in Canada, 95 severe covid-19 patients hospitalized in Vancouver were followed. Blood groups A and AB were more associated with a risk of acute disease progression, requiring more frequent assisted mechanical ventilation or dialysis for kidney failure. Besides, A and AB types tended to require more extended ICU stays than O or B blood types.
New hope from the U.S.
A joint team of experts led Sean Stowell, MD, Ph.D., from the Brigham and Women’s Hospital in Boston, worked to identify risk factors for severe COVID-19. Their findings were published on March 3, 2021, in the journal Blood Advances, which now confirms that certain blood types may be associated with an increased risk of contracting the disease.
The research suggests that the new coronavirus is particularly ‘attracted’ to the blood group A found in respiratory cells. In the study, the researchers evaluated a protein on the surface of the SARS-CoV-2 virus called the “receptor binding domain (RBD).” The RBD is the part of the virus that binds to host cells, making it a significant research target for understanding how infection occurs.
The team tested the blood groups on red blood cells and respiratory cells found in individuals of blood groups A, B, and O and analyzed how the virus RBD interacted with each blood type. The researchers found that the RBD had a strong preference’ to bind to the A blood group found in respiratory cells. However, Stowell and his team stressed that the findings alone could not fully describe or predict how the coronavirus may affect patients of various blood types.
While more research is needed to understand this influence, the article adds to the results of previous studies that suggest a possible link between blood type and COVID-19 susceptibility and severity.
Whatever the possible contribution of ABO(H) antigens to infection and possible disease progression, the ability of the SARS-CoV-2 to directly interact with the blood group A antigen uniquely expressed on respiratory epithelial cells provides clear evidence of a direct association between SARS-CoV-2 and the ABO(H) genetic locus.
The recent findings corroborate what science already knew. For instance, other viral infections, such as the Norwalk virus and hepatitis B, have an evident susceptibility to blood type, being more prevalent in some groups than others. Previous research has also shown that individuals with type O blood are less likely to be infected with SARS, another type of disease caused by coronaviruses.
More than one year has passed since the pandemic outbreak, and COVID-19 stands defiant in the face-off against the brightest scientific minds worldwide. Nevertheless, we are closer to solving the blood type conundrum even if we can’t change our blood type because it’s genetically inherited. “But if we can better understand how the virus interacts with blood groups in people, we may be able to find new medicines or methods of prevention.” That’s the message of hope in Dr. Sean Stowell’s words.
This article is for informational and entertainment purposes only. It only depicts my personal experience and should not be considered Health Advice. Please report to your local health authority for accurate and official guidance.
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