Serotype distribution among adults with community-acquired pneumococcal pneumonia in Japan between 2019 and 2022: A multicenter observational study
<i>Streptococcus pneumoniae</i> is a leading cause of community-acquired pneumonia (CAP) in adults. With the introduction of pneumococcal conjugate vaccines (PCVs) into pediatric national immunization programs, the serotype distribution of pneumococcal disease among adults has changed due to indirect effect. In Japan, PCV15 and PCV20 have been introduced, and PCV21 is under review for approval in adults. This multicenter observational study assessed pneumococcal serotypes in 583 adult patients with community-acquired, culture-positive pneumococcal pneumonia from May 2019 to December 2022. Pneumococcal isolates were serotyped using the Quellung reaction. The median patient age was 74 years (interquartile range: 66-82 years), 383 (65.7%) patients were male, 387 (66.4%) patients had one or more underlying medical conditions, 425 patients (72.9%) were hospitalized, and 305 (52.3%) had a CURB-65 score ≥2. The most common serotypes were serotype 3 (12.5%), 35B (12.0%), 15A (7.7%), 11A (6.7%), and 23A (6.3%). The proportion of serotypes covered by PCV13, PCV15, PCV20, PPSV23, and PCV21 were 24.0, 28.0, 43.7, 44.1, and 71.9%, respectively. The proportions of vaccine-covered serotypes were similar between patients aged <65 and ≥65 years. Serotype 3 was more prevalent among patients living in nursing homes (25.9%) compared with those living at home (11.2%). The proportions of PCV20- and PCV21-covered serotypes suggest that these new vaccines may offer additional protection against adult pneumococcal pneumonia. Given the availability of newly developed PCVs for adults in Japan, reassessing the optimal pneumococcal vaccination policy for adults is warranted.
Authors
- Atsushi Nakagawa (ORCID: https://orcid.org/0000-0002-1700-7861)
- Tomoyuki Urata
- Norichika Asoh
- Atsuhito Ushiki (ORCID: https://orcid.org/0000-0001-8158-6100)
- Issei Oi (ORCID: https://orcid.org/0000-0002-9624-7678)
- Bhim Gopal Dhoubhadel (ORCID: https://orcid.org/0000-0001-5279-2044)
- Yuko Toyoda (ORCID: https://orcid.org/0000-0002-9124-7978)
- Michiko Tsuchiya (ORCID: https://orcid.org/0009-0006-9699-4039)
- Kensuke Nishioka (ORCID: https://orcid.org/0000-0002-7473-6147)
- Mitsuhiro Tsukino
- Isao Ito (ORCID: https://orcid.org/0000-0003-3109-898X)
- Nobuyoshi Hamao (ORCID: https://orcid.org/0000-0002-0912-1963)
- Eiichiro Sando (ORCID: https://orcid.org/0000-0001-7824-5313)
- Masahiro Shirata (ORCID: https://orcid.org/0000-0002-5225-7911)
- Haruka Maeda (ORCID: https://orcid.org/0000-0002-0014-2602)
- Ai Yagiuchi
- Akira Nishiyama (ORCID: https://orcid.org/0000-0001-5971-820X)
- Takashi Yamada (ORCID: https://orcid.org/0000-0002-3133-1983)
- Toru Morikawa (ORCID: https://orcid.org/0000-0001-8014-5282)
- Akihiro Ito (ORCID: https://orcid.org/0000-0002-7508-0442)
- Konosuke Morimoto (ORCID: https://orcid.org/0000-0003-2912-9919)
- Tomoko Inoue (ORCID: https://orcid.org/0000-0001-5504-9352)
- Kayoko Okamura (ORCID: https://orcid.org/0000-0002-1241-4249)
- Yasuharu Nakahara
- Masayuki Ishida
- Yoshinori Hasegawa (ORCID: https://orcid.org/0000-0003-3841-4631)
- Hiroshi Fujii (ORCID: https://orcid.org/0000-0002-2720-5255)
- Naoki Sakai (ORCID: https://orcid.org/0000-0001-8544-1187)
- Takakazu Sugita
- Yusuke Kaji
- Yuya Fujii
- Seisuke Niibayashi
- Desmond Opoku Ntiamoah
Institutions
- Fukushima Medical University (JP)
- Shinshu University (JP)
- Tenri Hospital (JP)
- CHI Health (US)
- Kurashiki Central Hospital (JP)
- Rakuwakai Otowa Hospital (JP)
- Chikamori Hospital (JP)
- Akashi Municipal City Hospital (JP)
- Nara City Hospital (JP)
- Yokufukai Hospital (JP)
- Nagoya Ekisaikai Hospital (JP)
- Sapporo Minami Hospital (JP)
- Japanese Red Cross Kochi Hospital (JP)
- Himeji Medical Center (JP)
- Shizuoka City Hospital (JP)
- Otsu Red Cross Hospital (JP)
- Saiseikai Nakatsu Hospital (JP)
- National Hospital Organization (JP)
- Hikone Central Hospital (JP)
- Kobe City Medical Center West Hospital (JP)
- Kyoto University Hospital (JP)
- Japanese Red Cross Society Wakayama Medical Center (JP)
- Kitano Hospital (JP)
- Kobe City Medical Center General Hospital (JP)
- Ōtani University (JP)
- Nagasaki University (JP)
Publication Details
- Journal
- Human Vaccines & Immunotherapeutics
- Published
- 2025-06-27
- DOI
- https://doi.org/10.1080/21645515.2025.2518847
- Citations
- 2
- Primary Topic
- Pneumonia and Respiratory Infections
- Type
- article
- Field-Weighted Citation Impact
- 2.71
Funders
- Japan Society for the Promotion of Science