Editorial Response: Predicting Protection Against Encapsulated Pathogens.

Comments on the article of Sandra Romero-Steiner et al. in the August 1999 issue of 'Clinical Infectious Diseases' on the comparison of levels of capsule-specific immunoglobulin G (IgG) after pneumococcal vaccination in elderly and younger patients. Parameters which determine antibody avidity; Avidity of IgG for Streptococcus pneumoniae capsular polysaccharides; Duration of immune responses among the elderly patients following the vaccination.