For invasive isolates, PCV7 serotype coverage was 67% among children 60 months ( Table 1). Table 1 shows the serotype distributions of invasive and noninvasive isolates by age group. Overall, PCV7 serotypes accounted for 64.1% of total isolates and 62.7% of invasive isolates. Distribution of serotypes with regard to 7-valent conjugate vaccine (PCV7) among 538 isolates encountered during five 3-year periods from 1991 through 2006, South Korea.

pneumoniae serotype distribution changes in Korean children during 1991–2006 with an emphasis on serogroup 19.įigure 1. Surveillance since 1991 shows that serotype 19A isolates were increasingly recognized among clinical isolates before PCV7 was introduced in South Korea in November 2003. However, capsular switching of vaccine serotypes under selective pressure by PCV7 is one of the mechanisms underlying the expansion of serotype 19A ( 4, 11 – 13).Īs part of this surveillance implemented in a tertiary referral center in South Korea, all pneumococcal isolates obtained from sterile body fluids and from various clinical specimens were subjected to serotype and antimicrobial drug susceptibility pattern determinations ( 14). The direct effects of PCV7 in serotype distribution changes and genetic structures of pneumococcal isolates are not clear. In addition, recent studies from Massachusetts and Texas showed that a multidrug-resistant sequence type of serotype 19A has emerged as an important cause of IPD ( 9, 10). reported that serotype 19A was responsible for 28.3% of IPD in rural Alaska Native children <2 years of age during 2004–2006 ( 8). To date, replacement for IPD has been observed for serotypes 3, 15, 19A, 22F, 33F, and 35, with the increase in 19A being the most prevalent. However, the incidence of IPD caused by nonvaccine serotypes (including serotype 19A) increased 1.5-fold in 2002 compared to that in 1999 ( 2, 3). Since the introduction of 7-valent conjugate vaccine (PCV7) in the United States, a decrease in the incidence of invasive pneumococcal disease (IPD) caused by vaccine serotypes has been observed in pediatric and nonpediatric age groups ( 1, 2). Serotype incidence can vary by patient age, geographic region, and time of surveillance.

Among >90 serotypes, only a limited number account for pneumococcal diseases. Streptococcus pneumoniae is a major cause of invasive infections in young infants and children.

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