April 22, 2020

Is There a Link Between Blood Types and Coronavirus?

Blood type Coronavirus susceptibility

Blood type & Coronavirus susceptibility

A newly discovered link between blood types and coronavirus is all over the headlines. But can your blood type really make you more prone to COVID-19? We have summarized the latest findings to try and answer this question. Read on to learn the details!

This article is for informational purposes only. The current coronavirus outbreak is an ongoing event, and details may change as new information comes to light. There’s no firmly established connection between any blood type and COVID-19 susceptibility.

Blood Types and Antiviral Response

Before we dive into recent findings, let’s take a quick look at blood types and their potential influence on antiviral immunity.

What are the ABO Blood Types?

The ABO system is the most common way to classify blood in different groups. It’s based on the presence of specific carb molecules or ‘antigens’ on the surface of blood cells.

For example, someone with the A group only has “A” antigens. Their body recognizes “B” antigens and foreign substances and produces anti-B antibodies (see the image). That’s why it’s crucial to match these types during a blood transfusion.

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Source: https://en.wikipedia.org/wiki/ABO_blood_group_system

The Link With Antiviral Immunity

The idea that blood types can impact an antiviral response is nothing new. The A/B antigens are present on different cell types, and they can both inhibit or support viral infections. Anti-A/B antibodies can also play a role in antiviral responses [1, 2].

For example, norovirus, which causes digestive issues, can exploit these antigens in the gut to enter the body. People with the O group (no antigens) may be more resistant to infections in general. Those with the A group may be more prone to Hepatitis B and HIV viruses [3, 4].

Interestingly, back in 2005, scientists observed that people with the O group were more resistant to SARS coronavirus, which is similar to the new SARS-CoV-2 virus causing COVID-19 [5].

Different antigens and antibodies present in different blood types can inhibit or enhance viral infections. SARS-Cov infection has a potential link with blood types.

A Chinese Study Links Blood Types with COVID-19

Important: the findings below come from a “preprint” study that hasn’t been peer-reviewed. They remain inconclusive, unvalidated, and medically uncertain until the study undergoes peer review.

A group of Chinese authors combined the data from three hospitals and 2,173 total patients with COVID-19. By comparing the blood group distribution with that of a normal population, they found a significant link between two blood groups and infection rates. People with the A group were 21% more likely to become infected, while the O group was protective [6].

Confirmation from the US?

A recent preprint by the scientists from Columbia University investigated this link in 1,559 subjects, of which 682 were coronavirus-positive. They also found a higher frequency of the A group and a lower frequency of the O group among the infected people. However, the results were significant only for those with a positive Rh factor (Rh+) [7].

Potential Mechanisms

In 2008, researchers from France found that anti-A antibodies inhibited the binding of SARS coronavirus to ACE-2 receptors, thus reducing its potential to enter the cells [8].

They took a step further and created a mathematical model of virus transmission, taking into account different blood groups. According to the model, anti-A antibodies present in the B and O groups might significantly reduce virus transmission and the number of infected people [8].

Since the new coronavirus is similar to SARS-CoV and uses the same receptors, the authors of this Chinese study suggested the lack of anti-A antibodies as a potential risk factor for people with the A group [9, 10, 11].

However, a group from Belgium reanalyzed the 2020 Chinese data and found that the type of antibodies may also matter, which would explain why people with the O group seem to be protected against COVID-19 infection while those with the B group aren’t [12].

Whereas people with both group O and group B possess circulating anti-A antibodies, in people with the B group the anti-A antibodies are mostly IgM, which offer short-lived protection. In the O group, on the other hand, anti-A antibodies are IgG, the most prevalent antibodies in the body which offer long-term protection against viruses [12].

People with the A blood type might be more prone to COVID-19 due to the lack of protection by anti-A antibodies. Those with the O blood type may be somewhat protected thanks to their IgG anti-A antibodies. Further research is warranted.

Limitations

In addition to being a pre-print, this study has a few limitations worth mentioning [6]:

  1. Two out of three participating hospitals had a small number of patients.
  2. The study didn’t take into account other risk factors such as heart disease and diabetes.
  3. This kind of study can only find a correlation between blood types and COVID-19 and not the causative effect.

Keeping this in mind, we should wait for large, well-designed clinical trials before drawing any conclusions.

Takeaway

We classify ABO blood types by the presence of specific antigens and antibodies in the blood. These structures can both inhibit and enhance different viral infections.

Two recent studies found a potential link between blood types and COVID-19. People with the A group were more likely to get infected, while the O group was protective. The A group lacks anti-A antibodies, which may prevent coronavirus from entering the cells.

Due to a small sample and other limitations, we should wait for stronger clinical evidence before drawing any conclusions. If you carry the A blood type, there’s absolutely no reason to panic. Factors such as age, immunity, and other health conditions play a much more important role in your antiviral response.

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