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Updated: Feb 25, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Serotype replacement of Streptococcus pneumoniae due to seven-valent pneumococcal conjugate vaccine in Japan
Hiroshi Sakata1, Yoshitake Sato2, Yoshikiyo Toyonaga3
1Department of Pediatrics, Asahikawa Kosei Hospital, Asahikawa, Hokkaido, Japan.
Insights
The introduction of the seven-valent pneumococcal conjugate vaccine (PCV-7) in Japan led to significant shifts in Streptococcus pneumoniae serotypes. PCV-7 use decreased vaccine-targeted serotypes and increased non-vaccine types, indicating serotype replacement.
Area of Science:
- Microbiology
- Epidemiology
- Vaccinology
Background:
- Streptococcus pneumoniae serotypes causing infections in Japan were analyzed before and after the introduction of the seven-valent pneumococcal conjugate vaccine (PCV-7).
- Understanding serotype trends is crucial for evaluating vaccine impact and guiding public health strategies.
Purpose of the Study:
- To investigate the changes in S. pneumoniae serotype distribution in pediatric infections following PCV-7 implementation in Japan.
- To assess the impact of PCV-7 on the prevalence of vaccine-targeted and non-targeted serotypes.
Main Methods:
- Bacterial strains (458 in 2010, 370 in 2012) were collected from pediatric institutions across Japan.
- Samples were from children aged 0-14 years with various infections, including respiratory tract infections, meningitis, and sepsis.
- Serotype identification and statistical analysis were performed to compare pre- and post-vaccine introduction data.
Main Results:
- In 2010, serotypes 19F, 6B, and 23F were most common; by 2012, 6C, 19F, 15A, and 15B predominated, showing a significant shift.
- Prevalence of PCV-7 serotypes decreased from 61.1% in 2010 to 21.9% in 2012 (P < 0.01).
- Prevalence of PCV-13 serotypes also decreased significantly from 77.7% in 2010 to 39.5% in 2012 (P < 0.01).
Conclusions:
- Increased PCV-7 usage correlated with a reduction in PCV-7 and PCV-13 targeted serotypes.
- The observed changes suggest a phenomenon of serotype replacement, where non-vaccine serotypes increase as vaccine-targeted serotypes decrease.
- These findings highlight the dynamic impact of pneumococcal conjugate vaccines on circulating S. pneumoniae strains.
Background:
This study examined the trends for the serotypes of S. pneumoniae that have caused infections before (2010) and after (2012) the introduction of PCV-7 in Japan.
Methods:
We examined 458 strains of Streptococcus pneumoniae obtained from 22 pediatric institutions throughout Japan from January to June 2010 (immediately after the introduction of the seven-valent pneumococcal conjugate vaccine [PCV-7]), and 370 strains obtained from 19 institutions from January to June 2012 (after PCV-7 became widely used). The samples were collected from children aged 0-14 years with conditions such as respiratory tract infections (upper airway inflammation, bronchitis, and pneumonia), meningitis, and sepsis.
Results:
The most frequent serotype in the 2010 strains was 19F (17.3%), followed by 6B (16.8%), and 23F (15.1%). The most frequent serotype in the 2012 strains was 6C (10.0%), followed by 19F (9.7%), 15A (8.9%) and 15B (8.9%), indicating a significant change in the distribution. The serotypes contained in PCV-7 were detected in 280 strains (61.1%) in 2010 and in 81 strains (21.9%) in 2012 (P < 0.01). The serotypes contained in PCV-13 were detected in 356 strains (77.7%) in 2010 and in 146 strains (39.5%) in 2012 (P < 0.01). A total of 129 subjects who had not been vaccinated with PCV-7 and 127 subjects who had been vaccinated with PCV-7 at least once, were compared with regard to the 2012 strains. The serotypes contained in PCV-7 were found in 21 strains (16.5%) in those who had been vaccinated and in 37 strains (28.7%) in those who had not been vaccinated (P < 0.05).
Conclusions:
The increased use of PCV-7 led to decreases in the serotypes contained in PCV-13 and increases in the serotypes not contained in PCV-13, suggesting serotype replacement.
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