Background 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.
【저자키워드】 Influenza, influenza vaccine, vaccine effectiveness, multicentre study, case‐control study,