The study, entitled ‘The ABO blood group locus and a chromosome 3 gene cluster associate with SARS-CoV-2 respiratory failure in an Italian-Spanish genome-wide association analysis’, is a genome-wide association study (GWAS).
A GWAS looks for correlations between DNA markers (tiny mutations scattered throughout a person’s genome) and an outward physical or mental trait of some kind. In this case, that trait was extreme susceptibility to Covid-19, represented by respiratory failure.
As you might have guessed, when a GWAS is involved, ‘correlation’ is the keyword. A GWAS does not search for causation, and therefore it is only the first step in a process to find inherited factors behind physical, mental, or behavioral traits. Moreover, the paper has been published ahead of being peer reviewed on the pre-print server medRxiv, meaning its findings should be taken with a grain of salt.
Nevertheless, this is the first strong indication of genetic factors being at play in reaction to Covid-19.
Which blood type is best?
The study analyzed over eight and a half million mutations in total, and 1,725 Spaniards and 2,090 Italians from seven hotspots of coronavirus (Milan, Monza, Madrid, San Sebastian, and Barcelona) were included in the study. The researchers took efforts to exclude people of foreign ethnic origins so as to maintain as much homogeneity as possible in the database.
The study found that people with type A-positive blood are at higher risk of respiratory failure from Covid-19. Furthermore, those with type O blood are more protected from the virus. This was true for the cohort as a whole, as well as for the cohort when divided into Spain-only and Italy-only.