Background: Impaired ability to respond to polysaccharide capsular antigens of Streptococcus pneumoniae may be associated with an IgG subclass deficiency and recurrent respiratory infections.
Objective: To identify children over three years of age with recurrent otitis media, sinusitis, or pneumonia who had low or absent pneumococcal antibody titers as their sole manifestation of immune deficiency and to determine their response to the 23-valent pneumococcal vaccine.
Results: Of 100 children with low pneumococcal antibody titers, 87 generated a protective antibody response to the pneumococcal vaccine (> 300 ng/mL to the majority of the antigen serotypes), while 13 responded poorly or not at all. Repeated vaccination of nonresponders failed to produce a normal response.
Conclusion: We have identified two clinically distinct subpopulations of children with recurrent respiratory infections characterized by their responsiveness to pneumococcal antigens: one group did not respond to pneumococcal vaccination, whereas the other group responded both clinically and serologically. The nonresponding 6.5% subpopulation has an apparent isolated defect in anti-pneumococcal antibody production associated with recurrent respiratory infections despite normal IgG2 subclass levels.