Influenza vaccine 38% effective, saved 8K lives in 2017-2018 season

  • Rolfes MA & al.
  • Clin Infect Dis
  • 2 Feb 2019

  • curated by Liz Scherer
  • Clinical Essentials
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  • Despite 38% vaccine effectiveness (VE), influenza vaccination significantly reduced risk of any outpatient influenza-associated medically attended illness, A(H3N2) illness, and deaths during 2017-2018 season.

Why this matters

  • Vaccination remains one of the most important strategies to prevent influenza, related morbidity.
  • Encourage influenza vaccine uptake among all patients during routine visits.

Key results

  • 2017-2018 influenza-associated events: 47.9M illnesses, 22.1M medical visits, 953,000 hospitalizations, 79,400 deaths.
  • Adults aged >65 years: 15% of illnesses, 70%, 90% of hospitalizations, deaths, respectively.
  • A(H3N2) associated with highest illness rates.
  • 8436 U.S. Flu VE Network enrollees included: adjusted 38% (95% CI, 31%-43%) VE against influenza A or B.
  • VE varied by age group; adjusted VE for A(H3N2) was 22% (95% CI, 12%-31%), for A(H1N1)pdm09 62% (95% CI, 50%-71%), influenza B 50% (95% CI, 41%-57%).
  • Vaccination prevented 109,000 (95% credible intervals [Crl], 38,900-231,000) hospitalizations (10% of expected), 8000 (95% Crl, 1100-21,000) influenza-associated (9% expected) deaths overall, ~39% (95% Crl, 30%-45%) in children ages 6 months to 4 years.

Study design

  • 2017-2018 influenza season surveillance report assessing VE, influenza type/subtype-specific burden, and number of influenza-associated illnesses, medical visits, hospitalizations, deaths prevented by vaccination.
  • Funding: CDC.


  • Multipliers do not reflect current practice.
  • Subtype rate estimates imputed.
  • Waning VE unaccounted for.
  • Self-report bias.
  • Skewed credible intervals.

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