coronavirus & blood type: does it influence your COVID-19 immunity?

Recent studies show that people with type A blood may be more susceptible to COVID-19 illness than those with other blood types. Researchers in China reached this conclusion after studying 2,173 patients that had been treated in three Shenzhen and Wuhan hospitals for COVID-19, the illness caused by the SARS-CoV-2 virus.

The researchers looked at the distribution of blood types in the population of both cities and compared it with patients who had contracted the virus. Wuhan’s average population had a blood type distribution of 34% type O, 31% type A, 24% type B, and 9% type AB.

By comparison, those with the virus were distributed as follows: 38% type A, 26% type B, 25% type O, and 10% type AB. The statistics show that the greatest percentage of people who contracted the virus had type A blood.

Another study involving a review of medical records of 7,770 people that had tested positive for the SARS-CoV-2 virus found that those with:

• Type A blood were less likely to use/need a ventilator
• Type AB blood were more likely to use/need a ventilator
• Type O blood had a lower risk of contracting the virus

Do these study results mean that those with blood type O have some innate immunity to COVID-19? Not necessarily. These investigations were only preliminary and haven’t been peer-reviewed.

Correlation Between Blood Type and COVID-19

Scientists maintain that there isn't a strong enough connection between a person’s blood type and COVID-19 to consider blood type as a risk factor for contracting the virus. A possible correlation indicated by preliminary studies is tied to how different blood types develop antibodies as a patient’s immune system fights infection.

Typically, blood types are categorized based on the type of antigens contained in the blood. Blood is categorized as type A, B, AB, or O. When antigens come into contact with foreign substances, they trigger a response from the immune system. Such responses have been observed in medicine for some time. For example, problems have been seen during blood transfusions when the donor’s blood type doesn’t match the recipient’s.

Certain viruses appear to exploit the differences in blood cell antigens. For example, the norovirus infects people through the digestive system and needs specific antigens to “latch-on.” This may account for the difference in susceptibility to catching a virus.

A similar analogy can be used to explain the difference in COVID-19 infections in people with blood type A as opposed to other blood groups.

Blood type affects health in other ways beyond susceptibility to contracting viruses. Here are three ways that blood type can impact health:

1. Developing Heart Disease

Certain blood types have a higher risk of developing heart disease than others. People with blood type O have the lowest risk for heart disease. People with blood types AB and B have the greatest risk for developing heart disease. This is thought to be because these blood types typically have higher rates of inflammation. A heart-healthy lifestyle can be helpful for people with types AB and B blood. 

2. Different Types of Cancer

Blood types are also associated with different types of cancer. People with type A blood, for example, are more likely to develop stomach cancer than those with other blood types. The first notable study of this correlation can be traced back to 1953 when ABO blood-group distributions of 3,632 patients with gastric cancer were studied.

The researchers found a 20% increase in carcinoma of the stomach in patients with type A blood in comparison with the type O group of individuals. Another study conducted in 1961 found a positive correlation between blood group A and the risk of contracting stomach cancer.

Additional research shows that the ABO gene also increases the risk of developing other types of cancers, including liver, lung, breast, prostate, and cervical cancers. Most of these studies were performed using previous medical records that involved traditional blood collection methods (wet blood collection) instead of dried blood spot techniques.

3. Memory Loss and Brain Function

One study connects an individual’s blood type to an increased risk of developing memory loss. While people with blood type AB constitute the smallest percentage of the global population (4% in the US), 82% of people in the AB blood type group were more likely to develop cognition and memory problems.

A possible reason for this phenomenon is that blood type is associated with health conditions such as diabetes, high blood pressure, and high cholesterol, which are associated with cognitive impairment.

Further studies are needed to determine correlations between blood type and risk factors for disease. Future studies may utilize remote blood collection methods, such as the Mitra^® device with VAMS technology. Using remote blood sampling methods helps to expand the pool of study participants and, thus, gather more data.

For remote studies, participants can use the Mitra microsampling device at home to self-collect blood samples that can be mailed to the lab for testing. Researchers then analyze the dried blood samples to gather data. The data furnished by dried blood samples is typically either concordant with "wet" blood samples or can be correlated to traditional reference ranges.

The benefit of remote blood collection and dried blood analysis is that it eliminates the need for onsite facility visits and risky exposure to COVID-19 or other contagions. For future studies concerning blood types and viral immunity, researchers are likely to embrace remote sampling.

Because the findings regarding a possible correlation between blood types and immunity to COVID-19 are not conclusive, we should not assume that people of certain blood groups are more susceptible to the virus than others. What is known at this time, is that there are two factors that significantly increase the risk of contracting the virus:

1. An individual’s age (older people have a higher risk)
2. Underlying health conditions like cancer, chronic kidney disease, obesity, Type 2 diabetes, heart conditions, and sickle cell disease