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

• Main Author: Kissling, Esther
• Publication Date: 2019
• Other Authors: Pozo, Francisco, Buda, Silke, Vilcu, Ana-Maria, Gherasim, Alin, Brytting, Mia, Domegan, Lisa, Gómez, Verónica, Meijer, Adam, Lazar, Mihaela, Vučina, Vesna Višekruna, Dürrwald, Ralf, van der Werf, Sylvie, Larrauri, Amparo, Enkirch, Theresa, O’Donnell, Joan, Guiomar, Raquel, Hooiveld, Mariëtte, Petrović, Goranka, Stoian, Elena, Penttinen, Pasi, Valenciano, Marta, I-MOVE primary care study team
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.18/6536
• topic: Influenza; A(H3N2); Imprinting; Determinantes de Saúde e Doença; Estado de Saúde e Doença; Gripe; Vacina Antigripal; EuroEVA; Efetividade; Época 2018-2019

Introduction: Influenza 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). Aim: The 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. Methods: We 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. Results: Influenza 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-yearolds (1964–86) and 55–64-year-olds (1954–63), respectively. Discussion: The 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.