The genetic testing company 23andMe conducted a study in which 750,000 participants were involved. “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,” (Source)
“Individuals 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. “(Source)
Interestingly enough, the O-positive blood type is the most common in the world and the AB-negative type is the rarest