Nasopharyngeal Pneumococcal Carriage of Children Attending Day Care Centers in Korea: Comparison between Children Immunized with 7-valent Pneumococcal Conjugate Vaccine and Non-immunized

Abstract

To confirm the effect of 7-valent pneumococcal conjugate vaccine (PCV7), pneumococcal nasopharyngeal (NP) carriage was compared between vaccinated (3 + 1 doses PCV7) and non-vaccinated children. Vaccinated subjects were recruited from highly vaccinated regions (≥ 60%), Seoul and Incheon whereas control subjects were recruited from Jeju Island where vaccination rates are low (< 15%). NP swabs were obtained from 400 children aged 18-59 months. Serotype and antibiotic susceptibility was analyzed. Pneumococcal carriage rate was 18.0% (36/200) and 31.5% (63/200) for the vaccinated and control group, respectively. Among those vaccinated, 41.7% (15/36) of the serotypes were vaccine-related type (VRT: 6A, 6C, 19A) with the most common serotype 6C. The next common type was non-typable/non-capsule 30.6% (11/36) followed by non-vaccine type 16.7% (6/36) and vaccine type (VT) serotypes were found in only 11.1% (4/36). In contrast, 52.4% (33/63) of the isolates in the control group were VT. Resistance rates for penicillin and erythromycin were lower in the vaccine group (vaccine vs control; penicillin 45.2% vs 71.4%, erythromycin 74.2% vs 90.5%, P < 0.05). Multi-drug resistance was also lower in vaccinated subjects (vaccine vs control; 45.2% vs 69.8%, P < 0.05). PCV7 reduces carriage in VT which leads to replacement of pneumococci by antibiotic susceptible VRT or non-vaccine type strains.

Nontypeable Pneumococci Can Be Divided into Multiple cps Types, Including One Type Expressing the Novel Gene pspK

“…Sixteen Korean isolates were obtained from the nasopharynges (NP) of healthy children (less than 5 years old) attending daycare centers (DCCs) in 2008 (43). Twenty-six Brazilian isolates were obtained from the NP of children (less than 5 years old) attending municipal DCCs in 2005 (31, 45).…”

Changing Trends in Antimicrobial Resistance and Serotypes of Streptococcus pneumoniae Isolates in Asian Countries: an Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study

“…PCV7 was recently licensed and introduced into the Asian countries of South Korea (2003) (15). Although the PCV7 vaccination rate in most Asian countries has not been investigated, it seems to be very low in most Asian countries due to lack of awareness among both the general public and physicians and due to vaccination cost, while the vaccination rate in children under 5 years of age is relatively high in South Korea (over 60% in urban areas) (12). Vietnam, where PCV7 was not available at the time of the study, showed the highest coverage rate of PCV7 serotypes in this study, while the coverage rates have decreased in most other Asian countries compared with our previous studies.…”

Draft Genome Sequences of Five Multilocus Sequence Types of Nonencapsulated Streptococcus pneumoniae

“…The incidence of invasive pneumococcal disease (IPD) has significantly decreased since the introduction of conjugate vaccines based on seven, and more recently, 13 capsular polysaccharides (5, 6). However, the incidences of carriage and IPD have increased for some capsular serotypes not covered by the conjugate vaccines (7, 8), and the incidence of carriage has increased for nonencapsulated and nontypeable pneumococci (9, 10). …”