Background: The diagnosis of anti-polysaccharide antibody deficiency is based on the presence of normal serum immunoglobulin levels and the lack of specific antibody response to polysaccharide antigens, such as the pneumococcal vaccine. However, a normal response to pneumococcal vaccine is not well defined. "Modified meta-analysis" was undertaken in an attempt to define the normal antibody response to pneumococcal vaccine.
Methods: Studies identified by a MEDLINE search were selected. Data of the normal control groups, rather than the patient groups, were collated for analysis.
Results: Twenty-three studies fulfilled the selection criteria. Prevaccination antibody titers, postvaccination titers, and post- to prevaccination titer ratios varied widely. On the basis of weighted mean ratios, serotype 8 appeared to be the most antigenic. It appeared that normal subjects do not mount a response of even a twofold increase in antibody titer to all the serotypes present in the vaccine. Moreover, no minimal absolute antibody level that could be of diagnostic value, either before or after vaccination, was evident.
Conclusion: Response to pneumococcal vaccine among normal subjects varies widely. Better designed and prospective studies are needed to define the parameters of a normal antibody response to pneumococcal vaccine so that uniform guidelines of interpretation can be formulated.