Pneumococcal anticapsular antibodies in patients with chronic cardiovascular and obstructive lung disease in The Netherlands. Differences in pneumococcal anticapsular antibody concentrations were assessed among patients with various chronic disorders and among young (25-35 years of age) and older adults (55-65 years). Antibody concentrations were determined by ELISA, using the whole 23-valent pneumococcal polysaccharide vaccine as antigen. No differences in mean or distribution of serum antibody concentrations were found among young adults (either healthy or asthmatic) or among older adults (healthy or with chronic obstructive pulmonary or chronic cardiovascular disease). Each group included individuals with low antibody levels. Therefore, the enhanced susceptibility to pneumococcal infections reported for some groups at risk, that is, elderly individuals and patients with chronic obstructive pulmonary or chronic cardiovascular disease, cannot be attributed solely to low anticapsular antibody concentrations. 