Antibody response of young children to parenteral vaccination with pneumococcal capsular polysaccharides: a comparison between antibody levels in serum and middle ear effusion.

Total (radioimmunoassay) and immunoglobulin class-specific (enzyme-linked immunosorbent assay) antibodies to four pneumococcal capsular polysaccharide types were measured in serum and middle ear effusion (MEE) samples of 14 children who had received an injection of either a 14-valent pneumococcal capsular polysaccharide vaccine or a control, Haemophilus influenzae, type b capsular polysaccharide vaccine. Serum samples were collected before and 1 to 4 weeks after the vaccination and MEE samples at the time of the postvaccination serum. Only MEE negative for pneumococci by culture and antigen detection methods were included. Total and immunoglobulin G antibody to each of the four pneumococcal types correlated well between the corresponding serum and MEE samples. The quantity of such anti-pneumococcal antibodies in both the MEE and serum was usually larger in children who had received pneumococcal rather than control vaccine. Immunoglobulin M class antibodies seemed to penetrate poorly into the MEE. In some children, also the immunoglobulin A class antibodies in serum and MEE correlated well, whereas others had an aberrantly large amount of immunoglobulin A antibody in the MEE independent of the type of vaccine they had received, suggesting an ongoing local antibody response to a recent pneumococcal infection.