Investigation causes of the increasing non vaccine type pneumococcal infections after the introduction of pneumococcal conjugate vaccine

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K10097
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Pediatrics
• Research Institution: Chiba University
• Principal Investigator: Naruhiko Ishiwada 千葉大学, 真菌医学研究センター, 准教授 (30344980)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 肺炎球菌 / 13価肺炎球菌結合型ワクチン / 非PCV13含有血清型 / 免疫原性

Outline of Final Research Achievements

Nasopharyngeal carriage rate of Streptococcus pneumoniae in Japanese infants didn't change before and after the introduction of 13th-valent pneumococcal conjugate vaccine (PCV13).Among carriage pneumococcus strains, all strains changed non PCV13 serotypes and nontypeable S.pneumoniae strains increased after the introduction of PCV13. Clonally related serotype 12F,that is one of non PCV13 serotypes,increased the pathogen of invasive pneumococcal diseases (IPD) in Japan.
The titers of PCV13 serotype specific antibodies in non PCV13 immunized Japanese children with underlying disease was relatively lower than healthy Japanese children. This study result suggests that the recommendation of PCV13 is needed for non PCV13 immunized Japanese children with underlying diseases.The titers of non PCV13 serotype specific antibody in PCV13 immunized children with IPD were varied. The effects of PCV13 immunization against immune response of non PCV13 specific serotype pneumococcus was not clarified.

Free Research Field

細菌感染症

Academic Significance and Societal Importance of the Research Achievements

PCV13定期接種化後、PCV13含有血清型の侵襲性肺炎球菌感染症の激減と同時に、PCV13既接種乳児の鼻腔内肺炎球菌分離率は変わらないが、全てPCV13非含有血清型に変化していたことを証明したことは、PCV13定期接種化の効果とワクチン接種を継続する意義を明確にした。一方、同一性の高い血清型12Fや無莢膜株の顕在化は、継続した肺炎球菌サーベイランスの重要性を示唆するものであった。
本研究により基礎疾患を有する小児では、PCV13型肺炎球菌に対する免疫原性が低いことが明らかとなり、本邦においても肺炎球菌感染症ハイリスク小児に対してPCV13を積極的に勧奨すべき重要なデータと考えられた。