A person’s blood type doesn’t affect their risk of developing severe Covid-19 or of being hospitalized because of the infection, a study found.
Previous studies have shown that people with blood group A are more at risk of contracting the coronavirus.
To determine if this was true, U.S. doctors analyzed medical records of more than 100,000 people who had undergone a Covid-19 test in Utah, Idaho and Nevada between March and November 2020.
By comparing their Covid status to blood type, it was found that there was no relationship between the two, invalidating the earlier findings.
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People are more at risk of contracting the coronavirus if they have type A blood, a study found. Laboratory-based analysis examined previous reports that blood type affects an individual’s susceptibility to infection with SARS-CoV-2
Breakdown of British people by blood type
• O positive: 35%
• O negative: 13%
• A positive: 30%
• A negative: 8%
• B positive: 8%
• B negative: 2%
• AB positive: 2%
• AB negative: 1%
Source: 900,000 blood donors in the NHS blood and transplant registry
Blood type is a trait determined by a person’s DNA and depends on the versions of genes inherited from a person’s parents.
These genes dictate the presence of antigens on the surface of red blood cells, the donut-shaped vessels that carry oxygen around the body in arteries and veins.
Antigens are excellent proteins and there are two versions, A and B, which are found on the surface of red blood cells, also called erythrocytes.
Each person has A, B, A and B, or none. So these people have blood group A, B, AB and O respectively, and this is known as the ABO blood group system.
Another antigen on the cells called Rhesus is positive or negative and this determines whether a person is A positive or A negative, for example.
Blood types differ in their commonality depending on geography and ethnicity, but in the UK the most common group is O positive, followed by A positive.
Previous studies had shown that people with type A blood are at greater risk of contracting the virus.
The coronavirus SARS-CoV-2 has a higher affinity for other cells – such as those in the airways – that express a type A specific molecule called an antigen
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Scientists conducting the REMAP-CAP study stopped enrolling infected IC patients after finding “no evidence” that restorative plasma therapy increased survival.
The therapy has also been dropped by the world-leading RECOVERY study.
The former focuses on critically ill patients, while the latter concerns hospitalization, but not critically ill individuals.
The findings of the study trials are the deathblow for the once promising treatment touted by the NHS, NIH and academics.
One study hinted that type A people have more receptors the virus can bind to, making them more susceptible.
But Dr. Jeffrey Anderson, of the Intermountain Medical Center Heart Institute in Salt Lake City, conducted the most comprehensive and controlled analysis to date.
With conflicting reports from China, Europe, Boston, New York and elsewhere, we embarked on a large, prospective case-control study involving more than 11,000 individuals newly infected with SARS-CoV-2, and found no ABO associations with either disease susceptibility or severity, ”the study authors write in their paper, published today JAMA Network Open
“Given the extensive and prospective nature of our study and the strongly null results, we believe that significant associations of SARS-CoV-2 and Covid-19 with ABO groups are unlikely,” they add.
The researchers cannot explain why the earlier studies came to different conclusions, but cite several factors that may have led to the earlier results.
They say pure coincidence, publication bias, genetic differences, geography and variants may have led to biased data indicating that some blood types are more at risk.
However, the study found that while blood type does not, other factors do indeed increase the risk of Covid-19.
These include being male, being older and also people who are not of white descent.
“In people with Covid-19, hospitalization was associated with male gender and age,” the researchers write. “ICU admission was also associated with male gender and age.”
The data also showed that non-whites, including African Americans; American Indians or Alaskans; Native Hawaiian or Pacific Islanders; Asians; and people who have not disclosed their ethnicity are more likely to test positive.
However, there was no association between these people and the severity of the disease.
Earlier evidence of how blood type affects Covid
On March 17, 2020, just as the virus hit the UK and before the initial lockdown was introduced, MailOnline reported that Chinese researchers found that people with type A blood are significantly more likely to contract coronavirus than those with type O.
The Wuhan study also found that people with type A blood are more likely to die from COVID-19.
In the general population, Type O blood (34%) is more common than A (32%).
However, among COVID-19 patients, people with type O accounted for only 25%, while type A accounted for 41%.
People with type O blood made up a quarter (25 percent) of the deaths in the study. Typically, Type O people make up 32 percent of the people in Wuhan.
Researchers in China assessed 2,173 people diagnosed with the coronavirus, including 206 people who died after contracting the virus, from three hospitals in Hubei.
Academics compared the data from the infected Wuhan patients with 3,694 uninfected people in the same region.
Of the 206 patients in the study who died, 85 had type A blood, which is equivalent to 41 percent of all deaths.
In the healthy Wuhan population, a city of 11 million people, 34 percent of the people are type A.
In the study cohort, 52 of the people who died were type O, accounting for a quarter of all deaths. Under normal circumstances, only 32 percent of people are type O.
The figures for all infections, not just deaths, are 26 percent and 38 percent for type O and type A, respectively.
In November 2020, MailOnline again reported on a similar study that found that people with blood group A are more at risk.
Researchers at the Institute for Clinical Evaluative Sciences in Toronto studied 225,556 people who had a blood test between 2007 and 2019 and a Covid cotton swab in 2020.
One study found that people with blood group O are 12 percent less likely to contract the coronavirus than other blood types.
It also revealed that people with a negative blood type (O, A, B, or AB) are, on average, 21 percent less likely to get the virus than people with a positive blood type.
Individuals with type O or negative blood are also 13 percent and 19 percent less likely to develop severe symptoms or die, respectively.
In the UK, about 15 percent of the population has a negative blood type and nearly half (about 48 percent) are type O.
About one in eight people (13 percent) has O-, who are 26 percent less likely to get infected and 28 percent less likely to develop severe symptoms or die.