Trivalent inactivated influenza vaccine effective against influenza A(H3N2) variant viruses in children during the 2014/15 season, Japan

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 21; no. 42
• Main Authors: Sugaya, Norio, Shinjoh, Masayoshi, Kawakami, Chiharu, Yamaguchi, Yoshio, Yoshida, Makoto, Baba, Hiroaki, Ishikawa, Mayumi, Kono, Mio, Sekiguchi, Shinichiro, Kimiya, Takahisa, Mitamura, Keiko, Fujino, Motoko, Komiyama, Osamu, Yoshida, Naoko, Tsunematsu, Kenichiro, Narabayashi, Atsushi, Nakata, Yuji, Sato, Akihiro, Taguchi, Nobuhiko, Fujita, Hisayo, Toki, Machiko, Myokai, Michiko, Ookawara, Ichiro, Takahashi, Takao
• Format: Journal Article
• Language: English
• Published: Sweden European Centre for Disease Prevention and Control (ECDC) 20.10.2016
• Subjects: Adolescent; Antigens, Viral - immunology; Child; Child, Preschool; Female; Humans; Infant; Influenza A Virus, H3N2 Subtype - classification; Influenza A Virus, H3N2 Subtype - genetics; Influenza A Virus, H3N2 Subtype - immunology; Influenza A Virus, H3N2 Subtype - isolation & purification; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - epidemiology; Influenza, Human - genetics; Influenza, Human - immunology; Influenza, Human - prevention & control; Japan - epidemiology; Male; Population Surveillance; Respiratory Tract Infections - prevention & control; Respiratory Tract Infections - virology; Seasons; Surveillance and Outbreak Report; Treatment Outcome; Vaccination - statistics & numerical data; Vaccines, Inactivated; vaccine effectiveness; Influenza Virus; vaccine and immunization; Laboratory surveillance; Influenza
• ISSN: 1560-7917; 1025-496X; 1560-7917
• DOI: 10.2807/1560-7917.es.2016.21.42.30377

The 2014/15 influenza season in Japan was characterised by predominant influenza A(H3N2) activity; 99% of influenza A viruses detected were A(H3N2). Subclade 3C.2a viruses were the major epidemic A(H3N2) viruses, and were genetically distinct from A/New York/39/2012(H3N2) of 2014/15 vaccine strain in Japan, which was classified as clade 3C.1. We assessed vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children aged 6 months to 15 years by test-negative case-control design based on influenza rapid diagnostic test. Between November 2014 and March 2015, a total of 3,752 children were enrolled: 1,633 tested positive for influenza A and 42 for influenza B, and 2,077 tested negative. Adjusted VE was 38% (95% confidence intervals (CI): 28 to 46) against influenza virus infection overall, 37% (95% CI: 27 to 45) against influenza A, and 47% (95% CI: -2 to 73) against influenza B. However, IIV was not statistically significantly effective against influenza A in infants aged 6 to 11 months or adolescents aged 13 to 15 years. VE in preventing hospitalisation for influenza A infection was 55% (95% CI: 42 to 64). Trivalent IIV that included A/New York/39/2012(H3N2) was effective against drifted influenza A(H3N2) virus, although vaccine mismatch resulted in low VE.