Lack of Anti-A Haemagglutinin Response to Influenza Infection.

McDonald and Zuckerman have reported1 an excess of blood group O and a corresponding deficiency of group A among patients with influenza A2 infection. Blood group A-like antigens have been found in commercial influenza vaccines2, and injection of non-dialysable material from such vaccines has given 4- to 15-fold increases in anti-A titres3.