So let's move on to the next question, which is, is there any indication blood type influences
COVID-19 risk?
So based on some very small studies, just very limited evidence, there is some indication
that people with blood group A may have a higher risk of acquiring COVID-19 compared
to non-A blood groups.
Whereas individuals with blood type O may have a lower risk of the infection compared
to none-O blood groups.
So ABO blood groups have been involved in the susceptibility to other viral infections
in the related SARS-CoV-1 virus type A antibodies as found in people with type O or type B blood
types can provide protection by inhibiting the interaction of the virus with the ACE2
receptor.
So first, blood type is a classification of blood based on the presence or absence of
antibodies as well as inherited antigenic substances on the surface of red blood cells.
One of the most important blood type systems is the ABO system, and it's important to understand
that the ABO, so type A, type B, type O, or AB is the most dominant antigen.
So this is a signal that evokes an immune response that is present in blood cells.
This antigen type is essentially just a modified sugar.
So people with type A blood have a type A antigen on the surface of their cells, which
means they make antibodies against antigens that are tight B, because this is recognized
as not-self.
This is why a person with type A blood will reject a blood transfusion with a type B blood
type due to immune response.
So the body makes type B antibodies to attack that antigen and vice versa.
A person with type O blood, which is...I think it's the most common, does not express either
A or B antigen, therefore they make antibodies against both A and B antigens since they are
both considered foreign.
This means that people with type O blood can donate blood to a person with any blood types
since their blood cells do not express either A or B antigen.
It will not elicit an immune response.
But they can only receive blood from a person with type O since they make antibodies against
A and B antigens.
So, again, this very preliminary data suggest that people with type O blood may be less
susceptible to COVID-19 because they produce the type A antibodies, which are possibly
inhibiting the interaction between SARS-CoV-2 and the ACE2 receptor.
Now, that has been shown to be the case for SARS-CoV-1.
In one study investigating the relationship between ABO blood group and the COVID-19 susceptibility,
it was found that people with blood group A have a higher risk for acquiring COVID-19
compared to non-A blood groups, whereas blood groups O have a significantly lower risk for
the infection compared to non-O blood groups.
Another study, a retrospective analysis from clinical features in 101 death cases with
COVID-19, the ABO blood group distribution of deaths differed pretty remarkably between
that from the Han population in Wuhan.
Although not analyzed statistically, type O was comparatively low while type A was high.
It's possible that some of the protection for type O blood groups and some of the increased
risk for the type A blood groups may be similar to the mechanisms that have been seen with
SARS-CoV-1, namely the fact that type A antibodies have been shown to provide protection by inhibiting
the interaction between the SARS-CoV-1 virus and the ACE2 receptor, which is how the virus
gets entry into the cell.