Kissling, EstherValenciano, MartaPozo Sanchez, FranciscoVilcu, Ana-MariaReuss, AnnickaRizzo, CaterinaLarrauri, AmparoHorváth, Judit KrisztinaBrytting, MiaDomegan, LisaKorczyńska, MonikaMeijer, AdamMachado, AusendaIvanciuc, AlinaVišekruna Vučina, Vesnavan der Werf, SylvieSchweiger, BrunhildeBella, AntoninoGherasim, Alin ManuelFerenczi, AnnamáriaZakikhany, KatherinaO Donnell, JoanParadowska-Stankiewicz, IwonaDijkstra, FrederikaGuiomar, RaquelLazar, MihaelaKurečić Filipović, SanjaJohansen, KariMoren, Alain2020-04-282020-04-282018Influenza Other Respir Viruses. 2018 Jul;12(4):423-437.1750-2640http://hdl.handle.net/20.500.12105/9770BACKGROUND: During the 2015/16 influenza season in Europe, the cocirculating influenza viruses were A(H1N1)pdm09 and B/Victoria, which was antigenically distinct from the B/Yamagata component in the trivalent influenza vaccine. METHODS: We used the test-negative design in a multicentre case-control study in twelve European countries to measure 2015/16 influenza vaccine effectiveness (VE) against medically attended influenza-like illness (ILI) laboratory-confirmed as influenza. General practitioners swabbed a systematic sample of consulting ILI patients and a random sample of influenza-positive swabs was sequenced. We calculated adjusted VE against influenza A(H1N1)pdm09, A(H1N1)pdm09 genetic group 6B.1 and influenza B overall and by age group. RESULTS: We included 11 430 ILI patients, of which 2272 were influenza A(H1N1)pdm09 and 2901 were influenza B cases. Overall VE against influenza A(H1N1)pdm09 was 32.9% (95% CI: 15.5-46.7). Among those aged 0-14, 15-64 and ≥65 years, VE against A(H1N1)pdm09 was 31.9% (95% CI: -32.3 to 65.0), 41.4% (95% CI: 20.5-56.7) and 13.2% (95% CI: -38.0 to 45.3), respectively. Overall VE against influenza A(H1N1)pdm09 genetic group 6B.1 was 32.8% (95% CI: -4.1 to 56.7). Among those aged 0-14, 15-64 and ≥65 years, VE against influenza B was -47.6% (95% CI: -124.9 to 3.1), 27.3% (95% CI: -4.6 to 49.4) and 9.3% (95% CI: -44.1 to 42.9), respectively. CONCLUSIONS: Vaccine effectiveness (VE) against influenza A(H1N1)pdm09 and its genetic group 6B.1 was moderate in children and adults, and low among individuals ≥65 years. Vaccine effectiveness (VE) against influenza B was low and heterogeneous among age groups. More information on effects of previous vaccination and previous infection is needed to understand the VE results against influenza B in the context of a mismatched vaccine.engVoRhttp://creativecommons.org/licenses/by/4.0/Case-control studyInfluenzaInfluenza vaccineMulticentre studyVaccine effectivenessAdolescentAdultAgedCase-Control StudiesChildChild, PreschoolEuropeFemaleHumansInfantInfluenza A Virus, H1N1 SubtypeInfluenza B virusInfluenza VaccinesInfluenza, HumanMaleMiddle AgedYoung AdultAtribución 4.0 Internacional29125681124423-43710.1111/irv.125201750-2659Influenza and other respiratory virusesopen access