We investigated whether there had been any change in the epidemiology of Streptococcus pneumoniae in Korea before and after introduction of heptavalent pneumococcal conjugate vaccine(PCV7).

Between September 2001 and August 2006, clinical isolates were collected from patients with pneumococcal infection in Severance Hospital, Seoul, Korea. We analyzed trends in serotype distribution and antibiotic resistance before and after the introduction of PCV7.

There were 363 strains of Streptococcus pneumoniae isolated from clinical specimens; 143 before and 220 after PCV7 introduction. The predominant serotypes, in order of decreasing frequency, were 19F, 19A, 23F, 6B, 6A, 3, 9V, 14, 11A, 4, 29, and 18C; 152 isolates(41.9%) belonged to types included in PCV7. The proportion of clinical isolates that were nonsusceptible to penicillin increased from 58.8% in 2001 to 83.6% in 2006(P=0.046). There was no significant diminution in pneumococcal infection caused by vaccine serotypes after the introduction of PCV7. In children younger than age 2 years, the proportion of clinical isolates that were vaccine serotypes was higher than in persons older than age 15 years (59.3% vs 37.8%, P=0.004).

There was no significant diminution in pneumococcal infection caused by vaccine serotypes after the introduction of PCV7, therefore more universal pneumococcal immunization program is recommended especially for children younger than age 2 years.