Similar report in
Preliminary data from
23andMe's ongoing genetic study of
COVID-19 appears to lend more evidence for the importance of a
person's blood type - determined by the ABO gene - in differences in
the susceptibility to the virus.
23andMe is still
recruiting for its
massive study, most recently seeking
10,000 participants outside of 23andMe who have been
hospitalized and diagnosed with COVID-19.
have yet to finish looking at what the genetic data indicate.
But a first blush
look at the information from the more than 750,000 participants in
the study shows the following:
preliminary data suggest that O blood type appears to be
protective against the virus when compared to all other
with O blood type are between 9-18% percent less likely than
individuals with other blood types to have tested positive
for COVID-19, according to the data.
appeared to be little differences in susceptibility among
the other blood types.
findings hold when adjusted for age, sex, body mass index,
ethnicity, and co-morbidities.
one study (Testing the Association between Blood Type and COVID-19 Infection,
Intubation, and Death) found the blood group O only to be protective
across rhesus positive blood types, differences in rhesus
factor (blood type + or -) were not significant in 23andMe
data. Nor was this a factor in susceptibility or severity in
exposed to the virus - healthcare and other front line
workers - 23andMe found that blood type O is similarly
protective, but the proportion of cases within strata is
While it is still
very early in the study, 23andMe's preliminary investigation into
genetics seems to support these findings.
research participants who reported that they tested positive for
COVID-19 to those who tested negative, our researchers identified a
variant in the ABO gene associated with a lower risk.
nucleotide polymorphism in the ABO gene is rs505922, a T at that
location is associated with lower risk.
The P-value for
the association is 1.4e-8, OR = 0.88.
Both the data on
blood type and the preliminary genetic findings also appear to
support at least two recently published pre-print studies - one by
researchers in China (Relationship
between the ABO Blood Group and the COVID-19 Susceptibility) and the most recent one by
researchers in Italy and Spain (The
ABO Blood Group Locus and a Chromosome 3 Gene Cluster Associate with
SARSCoV-2 Respiratory Failure) - that look at the ABO gene's
role in COVID-19.
The study in China
looked at susceptibility, while the Italian and Spanish study found
an association with blood type and severity of the illness.
studies have reported that the ABO blood group plays a role in both
susceptibility and severity for COVID-19 (refs:
And we know from
other studies (Blood
Groups in Infection and Host Susceptibility)
the ABO blood group can play a direct role in other types of
infections by serving as receptors, or coreceptors for
microorganisms, parasites, and viruses...
findings from 23andMe's data are also notable because of the link
Comparing Blood Types
researchers wanted to investigate this link with blood type, so we
estimated the contribution to risk by comparing each blood group
against each of the others.
differences are quite small, an extremely large sample size is
needed to explore differences across groups.
study, which now includes more than 750,000 individuals, we
investigated the cumulative incidence of self-reported COVID-19 by
blood type, hospitalization by blood type, and proportion of those
infected after known exposure by blood type.
Here is what we
Percent of 23andMe research participants
who tested positive for COVID-19, by blood group.
respondents to the 23andMe COVID-19 survey, the percent of
respondents reporting a positive test for COVID-19 is lowest
for people who are O blood type.
of respondents reporting a positive test for COVID-19 was
highest among those with the AB blood type.
who were blood groups A, B, and AB did not statistically
differ from each other (Table 1 Below).
relationship holds after adjusting for age, sex, body mass
index, race, ethnicity, and co-morbidities.
Looking at Those
with Higher Probability for Exposure to COVID-19
this study found the blood group O protective only across
rhesus positive blood types, in 23andMe's data we found that
differences by self-reported
rhesus factor (blood type
+ or -) were not significant, nor was the
interaction between blood group and rhesus factor in
statistical models predicting being a case, or being a
understand the risk of acquiring the infection, we
restricted the data to those with a high probability
of exposure. This included professional health care
workers, those with close contact with known cases, and
As you can
see below, blood type O shows a similar pattern as seen
above, but the proportion of cases within strata is higher,
as we would expect.
Percent reporting positive test for COVID-19
among those with a high probability of exposure
(health care professionals, essential workers,
and those experiencing personal contact
with a diagnosed case),
by blood group.
for age, age squared, sex, race (census race categories), ethnicity
(Hispanic or Latino), BMI, and a single variable indicating a
vulnerability to severe infection (e.g. high-risk
co-morbidity or immunocompromised),
blood type O showed a protective
effect against both acquiring (OR = 0.86, p < 0.0001), and being
hospitalized for the infection (OR = 0.81, p = 0.05)...
effect of acquiring the infection strengthened in models restricted
to the "exposed" population (OR = 0.81, p < 0.0001). (Table 1
In the whole
population, those with the O blood group were 9-18% less likely to
test positive compared to the other groups.
When looking at
only exposed individuals, those with O blood group were 13-26% less
likely to test positive.
Adjusted Odds Ratios (ORs) and 95% Confidence Interval (CI)
estimating the effect of blood type O compared to
all other blood types for the risk of infection (case v control)
An OR is a statistic that quantifies the strength
of the association between a measurement and an outcome,
while a Confidence Interval is a range of values
that is likely to contain the true unknown value.
its COVID-19 study on April 6th, inviting customers to
participate in the large-scale study looking at whether genetics
could help explain the differences in severity among patients.
In early May, the
expanded to those outside of 23andMe who have experienced severe
in which 23andMe is providing 10,000 kits free of charge, aims to
identify individuals who tested positive and were hospitalized for
As part of the
research, participants answer survey questions about,
they've experienced cold or flu-like symptoms
they've been diagnosed or treated for COVID-19
they've been hospitalized for the illness
The study and
recruitment are ongoing, with the hope that we can use our research
platform to better understand differences in how people respond to
Ultimately, we hope
to publish our research findings in order to provide more insight
into COVID-19 for the scientific community.
How might we interpret
the practical implications of these results?
First, they do not tell
us that those with blood type 'O' aren't at risk of contracting,
falling ill, or dying from Covid-19. Neither do they tell us that
everyone with blood type 'A' who is infected will suffer respiratory
As far as we know,
everyone - regardless of blood type - is at risk of infection and