No. It is already known that type O people are at lower risk of disease, with higher risk to type B then higher still to type A then highest to type AB, and that when you do a GWAS study for associations with disease the ABO locus is one of exactly two loci that fall out as very important. The question is, is that due to some intrinsic degree of resistance to disease brought on by the ABO locus or is it due to this sort of transmission incompatibility? To know you need to figure out actual pairs of people you know transmitted to each other and see if particular pairwise patterns of blood types are more likely than others (which has never been done), and test the virions themselves to see that they can be neutralized by anti ABO antibody levels that you find in mucous membranes (though this is highly likely given previous work on other viruses).
So we can test AB-blood populations for antibodies and compare that to the general population, and you’ll know quickly if this theory is right or not?
No. It is already known that type O people are at lower risk of disease, with higher risk to type B then higher still to type A then highest to type AB, and that when you do a GWAS study for associations with disease the ABO locus is one of exactly two loci that fall out as very important. The question is, is that due to some intrinsic degree of resistance to disease brought on by the ABO locus or is it due to this sort of transmission incompatibility? To know you need to figure out actual pairs of people you know transmitted to each other and see if particular pairwise patterns of blood types are more likely than others (which has never been done), and test the virions themselves to see that they can be neutralized by anti ABO antibody levels that you find in mucous membranes (though this is highly likely given previous work on other viruses).