Polymorphism of human blood groups and incidence of influenza A/Hong Kong (H3N2).

During three epidemics of influenza A/Hong Kong (H3N2) and experimentally in vaccines, the relation between influenza infection and ABo, Rh and MN blood groups was studied. Examinations of 2760 patients with laboratory-confirmed diagnosis of influenza and 749 persons vaccinated with live influenza vaccine showed that individuals of blood groups O and B were susceptible to influenza 1.67 and 1.20 times more, respectively, than individuals of blood group A. The difference in incidence was most manifested in first attacks and decreased in subsequent epidemics. The increased incidence in individuals of blood groups O and B as compared to those of blood group A was not associated with factors of specific (antibody) and nonspecific (interferon) resistance to influenza but was related to a greater capacity of leukocytes from these individuals to adsorb the virus. No relation between blood groups Ph and MN and incidence of influenza A/Hong Kong (H3N2) was established.