Older adults should still receive influenza vaccination, even with seasonal mismatch

  • Rose AMC & al.
  • Influenza Other Respir Viruses
  • 05/02/2020

  • Liz Scherer
  • Clinical Essentials
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Takeaway

  • During the 2017-2018 influenza season, overall vaccine effectiveness (VE) against influenza A(H3N2) and B among older EU adults was only 24%.
  • Despite trivalent vaccine and circulating B mismatch, seasonal influenza VE (IVE) was still greater against influenza B vs A(H3N2), suggesting cross-protection.

Why this matters

  • Clinicians should encourage influenza vaccine uptake among older patients, even in seasons using trivalent vaccine with circulating influenza B lineage mismatch and adapted egg-propagated vaccine virus.

Key results

  • 3483 patients (1455 positive for any influenza type; 2028 negative):
    • 376 influenza A(H3N2), 299 influenza B/Yamagata, 26 B/Victoria.
  • Influenza A(H3N2):
    • Pooled adjusted IVE: 24% (95% CI, 2%-40%).
    • IVE by age: 
      • 35% (6%-55%) for age 65-79 years, vs
      • 14% (−22% to 39%) for age ≥80 years.
  • Influenza B:
    • Pooled adjusted IVE: 30% (95% CI, 16%-41%).
    • IVE by age:
      • 37% (19%-51%) for 65-79 years, vs
      • 19% (−7% to 38%) for ≥80 years.
  • ~2 of 3 of patients with influenza had underlying cardiovascular disease.

Study design

  • Prospective, test-negative design, pooled analysis of 2017-2018 seasonal IVE against hospitalization with influenza A(H3N2), influenza B among older, hospitalized adults age ≥65 years, by age group, comorbidities, and prior season vaccination across 9 EU countries, 2017-2018.
  • Funding: Horizon 2020.

Limitations

  • Small sample size.
  • Possible misclassification bias.