Does Your Blood Type Affect Your Risk of Covid-19? An intriguing study published last week found a link between covid-19 severity and having type A blood; type O blood, on the other hand, was linked to a lower chance of severe illness. But it’s unlikely that any potential connection between covid-19 and blood type will be very relevant to the average person.The study, published in the New England Journal of Medicine, involved nearly 2,000 severely ill covid-19 patients in Spain and Italy. Researchers looked at these people’s genetic code, in what’s known as a genomewide association study, or GWAS. They compared their genetics to the genetics of a similar control group, looking for any differences that could plausibly influence someone’s risk of catching the infection or having a more serious case.