Pneumococcal vaccination is advocated for asthmatics. Although routinely performed, data supplying evidence for this recommendation are limited. We examined the immunological background of 215 asthmatic children (2-5 year old) at a university children's hospital and compared the immunogenicity of the recommended pneumococcal vaccines. Testing encompassed serum immunoglobulins, immunoglobulin G (IgG)-subclasses, and pneumococcal antibodies against serotypes 4, 6B, 9V, 14, 18C, 19F and 23F. An infection-prone subgroup received one dose of 23-valent pneumococcal polysaccharide vaccine (PPV-23; n = 38, median age 45 months) or of 7-valent conjugate vaccine (PCV-7; n = 23; median age 35 months). Pneumococcal antibodies were determined again after 4 weeks. Low immunoglobulin- and/or IgG-subclass levels were found in 27 subjects (14 infection-prone). Prevaccination pneumococcal antibody levels ranged from 0.36 to 1.06 microg/ml, depending on the serotype. The percentage of subjects with putative protective antibody levels > or =1.0 microg/ml ranged only from 19.9% to 54.1%, over all. Postvaccination, antibody geometric mean concentrations increased significantly higher in PCV-7 vaccinees for serotype 14 (p < 0.01) and 23F (p < 0.05). Now the percentage of putatively protected subjects ranged from 40.9% (serotype 6B) to 90.9% (serotype 19F) following PCV-7 compared with 31.6% (serotype 6B and 23F) to 81.6% (serotype 19F) in PPV-23 vaccinees. Our data give further evidence for pneumococcal vaccination of asthmatic children. PCV-7 is at least as immunogenic as PPV-23. Moreover, for children suffering from persistent asthma, PCV immunisation should be considered.