IgA, IgG and IgM anti-blood group A antibodies induced by pneumococcal vaccine.

Pneumococcal polysaccharide vaccine contaminated with blood group A-like substance stimulated long-lasting production of anti-A antibodies in 10 of 11 subjects with O or B blood group. ELISA using blood group A substance as antigen detected increased IgA anti-A levels 18 months after vaccination in 82% of O and B subjects, the corresponding values being 73% for IgG and 18% for IgM. In females of O or B blood group becoming pregnant with a fetus of group A or AB, prior immunization to blood group A substance may cause a potential risk for haemolytic disease of the newborn.