Incidence of invasive pneumococcal disease and distribution of capsular types of pneumococci in Denmark, 1989-94

During the period 1989-94, 4620 strains of Streptococcus pneumoniae (4063 from blood and 557 from cerebrospinal fluid), from cases of invasive disease in Denmark, were received for capsular typing and penicillin susceptibility testing. During the study period the incidence of bacteraemic pneumococcal disease increased from 10 to 18 cases per 100000 inhabitants per year. The highest rates were seen in the very young, age less than 5 years (23/100000/year, in 1994), and in the elderly, age greater than 60 years (55/100000/year, in 1994). The annual number of cases of meningitis did not vary. Overall, 92% (93% blood, 87% CSF) of isolates and 94% of all childhood isolates belonged to the 23 vaccine types. The capsular types occurring most commonly among the 4123 pneumococcal strains from adults were types 1, 4, 14, 6A + 6B, 7F, 9V, 3, 12F, and 8 (in order of frequency). The ten most frequently occurring types from children (6A + 6B, 18C, 14, 1, 7F, 19F, 9V, 4, and 23F) covered 84% of the cases of bacteraemia and meningitis. Reduced susceptibility to penicillin was rare (< 1%).