Patients with Type A blood seem to be at greater risk of heavy complications from Covid-19

"Having Type A blood was linked to a 50 percent increase in the likelihood that a patient would need to get oxygen or to go on a ventilator, according to the new study.  

The doctors took blood samples from 1,610 patients who needed an oxygen supply or had to go on a ventilator. Dr. Franke and his colleagues extracted DNA from the samples and scanned it using a rapid technique called genotyping.


The researchers did not sequence all three billion genetic letters in the genome of each patient. Instead, they looked at nine million letters. Then the researchers carried out the same genetic survey on 2,205 blood donors with no evidence of Covid-19.

The scientists were looking for spots in the genome, called loci, where an unusually high number of the severely ill patients shared the same variants, compared with those who were not ill.

Two loci turned up. In one of these sites is the gene that determines our blood type. That gene directs production of a protein that places molecules on the surface of blood cells.


It’s not the first time Type A blood has turned up as a possible risk. Chinese scientists who examined patient blood types also found that those with Type A were more likely to develop a serious case of Covid-19.

No one knows why.

The locus where the blood-type gene is situated also contains a stretch of DNA that acts as an on-off switch for a gene producing a protein that triggers strong immune responses. The coronavirus triggers an overreaction of the immune system in some people, leading to massive inflammation and lung damage — the so-called cytokine storm. It is theoretically possible that genetic variations influence that response.


A second locus, on Chromosome 3, shows an even stronger link to Covid-19. But that spot is home to six genes, and it is not yet possible to say which of them influences the course of Covid-19.


One of those gene candidates encodes a protein known to interact with ACE2, the cellular receptor needed by the coronavirus to enter host cells. But another gene nearby encodes a potent immune-signaling molecule. It is possible that this immune gene also triggers an overreaction that leads to respiratory failure.


Previous attempts to find any genetic loci that varied significantly between sick people and healthy ones have failed. It is possible to speculate that the new study succeeded because the researchers focused only on people who had respiratory failure and were clearly vulnerable to serious forms of Covid-19."