Case report on a defective antibody response against pneumococcal serotype 9V in a patient with a single episode of pneumonia.

Background: Patients with recurrent respiratory tract infections and an impaired response to pneumococcal polysaccharide vaccination are diagnosed with a specific antibody deficiency. In adult patients with pneumococcal pneumonia an impaired antibody response to the infecting pneumococcal serotype can sometimes be found. It is unknown whether these patients are unable to produce an adequate anti-polysaccharide antibody response to pneumococcal vaccination after recovery.

Case presentation: The authors describe a case of invasive pneumonia caused by Streptococcus pneumoniae serotype 9V in a previously healthy 35-year-old female. This patient did not produce serotype-specific antibodies against the infecting serotype during disease. After pneumococcal polysaccharide vaccination 3 months after recovery, she responded adequately to most other pneumococcal serotypes, but still had no response to the infecting serotype 9V. However, after 9 years (and prior to pneumococcal-conjugate vaccination) normal antibody levels against 9V were found. These antibody levels further increased after pneumococcal-conjugate vaccination.

Conclusion: The authors believe that this case is the first description of a temporary deficient response to the infecting pneumococcal serotype in adults, while other reports with similar observations all involved children.