Effectiveness of inactivated and live-attenuated influenza vaccines in children during the 2025–2026 influenza season with genetically distinct influenza A and B viruses
As part of ongoing surveillance since the 2013/14 season, we evaluated influenza vaccine performance among children in Japan during the 2025/26 season, when subclade K A(H3N2) predominated. A test-negative design was applied to hospitalized febrile children who underwent outpatient influenza testing at 16 hospitals. Among 1033 participants, vaccine uptake among test-negative controls was 38% (274/723) for inactivated influenza vaccine (IIV) and 5% (35/723) for live-attenuated influenza vaccine (LAIV). Adjusted VE against influenza A was estimated at 43% (95% CI: 15-62) for IIV (N = 922) and 81% (95% CI: 15-96) for LAIV (N = 640), although the number of LAIV recipients was relatively small. No significant protection was observed against influenza B. These findings indicate that both vaccines remained effective against influenza A, despite circulation of genetically distinct influenza A viruses. Continued surveillance is warranted to further clarify comparative effectiveness between vaccine types as LAIV uptake increases.
Authors
- Naonori Maeda (ORCID: https://orcid.org/0000-0001-8799-288X)
- Ryunosuke Sugimoto
- Akifumi Tokita (ORCID: https://orcid.org/0009-0000-7023-4425)
- Masayoshi Shinjoh (ORCID: https://orcid.org/0000-0002-6291-7186)
- Munehiro Furuichi (ORCID: https://orcid.org/0000-0001-7742-1135)
- Go Yamada (ORCID: https://orcid.org/0000-0003-3122-2418)
- Satoshi Narumi (ORCID: https://orcid.org/0000-0002-0940-4517)
- Kiyoko Iwatsuki‐Horimoto (ORCID: https://orcid.org/0000-0002-8266-020X)
- Mitsuhiro Nishida (ORCID: https://orcid.org/0000-0003-2016-3598)
- Kenichiro Tsunematsu
- Akinobu Kamei
- Hiroyuki Fukushima (ORCID: https://orcid.org/0000-0003-3869-9892)
- Norio Sugaya
- Atsushi Narabayashi (ORCID: https://orcid.org/0000-0002-5274-8104)
- Yuki Tsumura
- M. Tezuka
- Yoshio Yamaguchi (ORCID: https://orcid.org/0000-0003-4144-8760)
- Michiko Chiga (ORCID: https://orcid.org/0000-0002-0346-9352)
- Mizuki Yaginuma (ORCID: https://orcid.org/0000-0002-6335-360X)
- Makoto Yoshida (ORCID: https://orcid.org/0000-0002-2846-2069)
- Ryo Itaki
- Akimichi Shibata
- Chiharu Kawakami
- Gembu Otsubo
- Chieko Kusano
- Yoshihiro Kawaoka
- Kiyomi Abe
Institutions
- National Institute of Infectious Diseases (JP)
- National Defense Medical College Hospital (JP)
- Hiratsuka City Hospital (JP)
- Ashikaga Red Cross Hospital (JP)
- Shizuoka City Shimizu Hospital (JP)
- National Center for Global Health and Medicine (JP)
- Tokyo Medical Center (JP)
- Tokyo Dental College Ichikawa General Hospital (JP)
- Keio University Hospital (JP)
- Kawasaki Municipal Hospital (JP)
- Sapporo Kosei General Hospital (JP)
- Nagano Municipal Hospital (JP)
- Saitama Municipal Hospital (JP)
- Yokohama Municipal Citizen's Hospital (JP)
- Fuji Heavy Industries Health Insurance Society Ota Memorial Hospital (JP)
- Minamiaoyama Eye Clinic (JP)
- Otsuka Pharmaceutical (Spain) (ES)
- keiyu Hospital (JP)
- Tochigi Medical Center (JP)
- Social Insurance Saitama Chuo Hospital (JP)
- Toshima Hospital (JP)
- National Defense Medical College (JP)
- The University of Tokyo (JP)
Publication Details
- Journal
- Vaccine
- Published
- 2026-06-25
- DOI
- https://doi.org/10.1016/j.vaccine.2026.128869
- Primary Topic
- Influenza Virus Research Studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00