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Vaccine
. 2024 Aug 22;42(23):126241.
doi: 10.1016/j.vaccine.2024.126241. Online ahead of print. Effectiveness of inactivated influenza vaccine in children during the 2023/24 season: The first season after relaxation of intensive COVID-19 measures
Masayoshi Shinjoh 1 , Mizuki Yaginuma 2 , Yoshio Yamaguchi 3 , Kazuyo Tamura 4 , Munehiro Furuichi 2 , Yuki Tsumura 5 , Ryo Itaki 6 , Asef Iqbal 7 , Naonori Maeda 8 , Atsushi Narabayashi 9 , Akinobu Kamei 9 , Akimichi Shibata 10 , Go Yamada 11 , Mitsuhiro Nishida 12 , Tsunematsu Kenichiro 13 , Michiko Chiga 6 , Motoko Shimoyamada 14 , Makoto Yoshida 15 , Naoya Fukushima 16 , Yuji Nakata 4 , Hiroyuki Fukushima 17 , Chiharu Kawakami 18 , Satoshi Narumi 2 , Norio Sugaya 19 ; Keio Pediatric Influenza Research Group
Affiliations
Background: The annual administration of the influenza vaccine is the most effective method for preventing influenza. We have evaluated the effectiveness of the inactivated influenza vaccine in children aged 6 months to 15 years across the seasons from 2013/2014 to 2022/2023. This study aims to investigate the effectiveness of the inactivated influenza vaccine in the 2023/2024 season, the first year following the easing of strict COVID-19 measures, and possibly the last season when only the inactivated vaccine is available on the market.
Methods: Adjusted vaccine effectiveness for the 2023/2024 season was assessed using a test-negative case-control design, with results based on polymerase chain reaction and rapid influenza diagnostic tests. Vaccine effectiveness was calculated by influenza type and patient hospitalization/outpatient status.
Results: A total of 1832 children were recruited. The inactivated influenza vaccine was effective in preventing both symptomatic influenza A and B in both inpatient and outpatient settings. Overall vaccine effectiveness for influenza A was 51% (95% confidence interval [CI], 23%-69%, n = 930) in inpatient settings and 54% (95%CI, 27%-71%, n = 559) in outpatient settings. For influenza B, effectiveness was 60% (95%CI, 22%-79%, n = 859) in inpatient settings and 56% (95%CI, 26%-74%, n = 558) in outpatient settings. Analysis suggested that administering two doses enhanced effectiveness specifically against influenza B.
Conclusions: This is the first study to demonstrate influenza vaccine effectiveness in children after the relaxation of strict COVID-19 measures in Japan (2023/2024). We recommend the current inactivated vaccine for preventing both influenza A and B in children, with consideration for the potential use of two doses to enhance effectiveness against influenza B.
Keywords: Children; Inactivated vaccine; Influenza; Test-negative design; Vaccine; Vaccine effectiveness.
. 2024 Aug 22;42(23):126241.
doi: 10.1016/j.vaccine.2024.126241. Online ahead of print. Effectiveness of inactivated influenza vaccine in children during the 2023/24 season: The first season after relaxation of intensive COVID-19 measures
Masayoshi Shinjoh 1 , Mizuki Yaginuma 2 , Yoshio Yamaguchi 3 , Kazuyo Tamura 4 , Munehiro Furuichi 2 , Yuki Tsumura 5 , Ryo Itaki 6 , Asef Iqbal 7 , Naonori Maeda 8 , Atsushi Narabayashi 9 , Akinobu Kamei 9 , Akimichi Shibata 10 , Go Yamada 11 , Mitsuhiro Nishida 12 , Tsunematsu Kenichiro 13 , Michiko Chiga 6 , Motoko Shimoyamada 14 , Makoto Yoshida 15 , Naoya Fukushima 16 , Yuji Nakata 4 , Hiroyuki Fukushima 17 , Chiharu Kawakami 18 , Satoshi Narumi 2 , Norio Sugaya 19 ; Keio Pediatric Influenza Research Group
Affiliations
- PMID: 39178768
- DOI: 10.1016/j.vaccine.2024.126241
Background: The annual administration of the influenza vaccine is the most effective method for preventing influenza. We have evaluated the effectiveness of the inactivated influenza vaccine in children aged 6 months to 15 years across the seasons from 2013/2014 to 2022/2023. This study aims to investigate the effectiveness of the inactivated influenza vaccine in the 2023/2024 season, the first year following the easing of strict COVID-19 measures, and possibly the last season when only the inactivated vaccine is available on the market.
Methods: Adjusted vaccine effectiveness for the 2023/2024 season was assessed using a test-negative case-control design, with results based on polymerase chain reaction and rapid influenza diagnostic tests. Vaccine effectiveness was calculated by influenza type and patient hospitalization/outpatient status.
Results: A total of 1832 children were recruited. The inactivated influenza vaccine was effective in preventing both symptomatic influenza A and B in both inpatient and outpatient settings. Overall vaccine effectiveness for influenza A was 51% (95% confidence interval [CI], 23%-69%, n = 930) in inpatient settings and 54% (95%CI, 27%-71%, n = 559) in outpatient settings. For influenza B, effectiveness was 60% (95%CI, 22%-79%, n = 859) in inpatient settings and 56% (95%CI, 26%-74%, n = 558) in outpatient settings. Analysis suggested that administering two doses enhanced effectiveness specifically against influenza B.
Conclusions: This is the first study to demonstrate influenza vaccine effectiveness in children after the relaxation of strict COVID-19 measures in Japan (2023/2024). We recommend the current inactivated vaccine for preventing both influenza A and B in children, with consideration for the potential use of two doses to enhance effectiveness against influenza B.
Keywords: Children; Inactivated vaccine; Influenza; Test-negative design; Vaccine; Vaccine effectiveness.