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. 2019 Nov;24(48):1900604.
doi: 10.2807/1560-7917.ES.2019.24.48.1900604.

Low 2018/19 vaccine effectiveness against influenza A(H3N2) among 15-64-year-olds in Europe: exploration by birth cohort

Esther Kissling  1 , Francisco Pozo  2 , Silke Buda  3 , Ana-Maria Vilcu  4 , Alin Gherasim  5   6 , Mia Brytting  7 , Lisa Domegan  8   9 , Verónica Gómez  10 , Adam Meijer  11 , Mihaela Lazar  12 , Vesna Višekruna Vučina  13 , Ralf Dürrwald  14 , Sylvie van der Werf  15   16 , Amparo Larrauri  5   6 , Theresa Enkirch  7 , Joan O'Donnell  8 , Raquel Guiomar  17 , Mariëtte Hooiveld  18 , Goranka Petrović  13 , Elena Stoian  12 , Pasi Penttinen  19 , Marta Valenciano  1 ; I-MOVE primary care study team  20
Affiliations

Low 2018/19 vaccine effectiveness against influenza A(H3N2) among 15-64-year-olds in Europe: exploration by birth cohort

Esther Kissling et al. Euro Surveill. 2019 Nov.

Abstract

IntroductionInfluenza A(H3N2) clades 3C.2a and 3C.3a co-circulated in Europe in 2018/19. Immunological imprinting by first childhood influenza infection may induce future birth cohort differences in vaccine effectiveness (VE).AimThe I-MOVE multicentre primary care test-negative study assessed 2018/19 influenza A(H3N2) VE by age and genetic subgroups to explore VE by birth cohort.MethodsWe measured VE against influenza A(H3N2) and (sub)clades. We stratified VE by usual age groups (0-14, 15-64, ≥ 65-years). To assess the imprint-regulated effect of vaccine (I-REV) hypothesis, we further stratified the middle-aged group, notably including 32-54-year-olds (1964-86) sharing potential childhood imprinting to serine at haemagglutinin position 159.ResultsInfluenza A(H3N2) VE among all ages was -1% (95% confidence interval (CI): -24 to 18) and 46% (95% CI: 8-68), -26% (95% CI: -66 to 4) and 20% (95% CI: -20 to 46) among 0-14, 15-64 and ≥ 65-year-olds, respectively. Among 15-64-year-olds, VE against clades 3C.2a1b and 3C.3a was 15% (95% CI: -34 to 50) and -74% (95% CI: -259 to 16), respectively. VE was -18% (95% CI: -140 to 41), -53% (95% CI: -131 to -2) and -12% (95% CI: -74 to 28) among 15-31-year-olds (1987-2003), 32-54-year-olds (1964-86) and 55-64-year-olds (1954-63), respectively.DiscussionThe lowest 2018/19 influenza A(H3N2) VE was against clade 3C.3a and among those born 1964-86, corresponding to the I-REV hypothesis. The low influenza A(H3N2) VE in 15-64-year-olds and the public health impact of the I-REV hypothesis warrant further study.

Keywords: A(H3N2); birth cohorts; imprinting; influenza; multicentre study; vaccine effectiveness.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Number of ILI patients by influenza A(H3N2) status (test-negative controls and A(H3N2) cases) and week of symptom onset, I-MOVE primary care multicentre study, Europe, influenza season 2018/19 (n = 6,172)
Figure 2
Figure 2
Birth cohort-specific vaccine effectiveness against influenza A(H3N2), I-MOVE primary care multicentre study, Europe, influenza season 2018/19 (n = 5,802)
See this image and copyright information in PMC

References

    1. European Centre for Disease Prevention and Control (ECDC), World Health Organization Regional Office for Europe (WHO/Europe). Flu News Europe. Summary week 20/2019 (13-20 May 2019). 13-May-2019. Stockholm: ECDC; 2019. Available from: https://flunewseurope.org/Archives/GetFile?fileId=422
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    1. Kissling E, Valenciano M, Pozo F, Vilcu AM, Reuss A, Rizzo C, et al. 2015/16 I-MOVE/I-MOVE+ multicentre case-control study in Europe: Moderate vaccine effectiveness estimates against influenza A(H1N1)pdm09 and low estimates against lineage-mismatched influenza B among children. Influenza Other Respir Viruses. 2018;12(4):423-37. 10.1111/irv.12520 - DOI - PMC - PubMed
    1. Kissling E, Pozo F, Buda S, Vilcu AM, Rizzo C, Gherasim A, et al. Effectiveness of influenza vaccine against influenza A in Europe in seasons of different A(H1N1)pdm09 and the same A(H3N2) vaccine components (2016-17 and 2017-18). Vaccine X. 2019;3:100042. 10.1016/j.jvacx.2019.100042 - DOI - PMC - PubMed

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