2012-2013 Seasonal influenza vaccine effectiveness against influenza hospitalizations: results from the global influenza hospital surveillance network

PLoS One. 2014 Jun 19;9(6):e100497. doi: 10.1371/journal.pone.0100497. eCollection 2014.


Background: The effectiveness of currently licensed vaccines against influenza has not been clearly established, especially among individuals at increased risk for complications from influenza. We used a test-negative approach to estimate influenza vaccine effectiveness (IVE) against hospitalization with laboratory-confirmed influenza based on data collected from the Global Influenza Hospital Surveillance Network (GIHSN).

Methods and findings: This was a multi-center, prospective, active surveillance, hospital-based epidemiological study during the 2012-2013 influenza season. Data were collected from hospitals participating in the GIHSN, including five in Spain, five in France, and four in the Russian Federation. Influenza was confirmed by reverse transcription-polymerase chain reaction. IVE against hospitalization for laboratory-confirmed influenza was estimated for adult patients targeted for vaccination and who were swabbed within 7 days of symptom onset. The overall adjusted IVE was 33% (95% confidence interval [CI], 11% to 49%). Point estimates of IVE were 23% (95% CI, -26% to 53%) for influenza A(H1N1)pdm09, 30% (95% CI, -37% to 64%) for influenza A(H3N2), and 43% (95% CI, 17% to 60%) for influenza B/Yamagata. IVE estimates were similar in subjects <65 and ≥65 years of age (35% [95% CI, -15% to 63%] vs.31% [95% CI, 4% to 51%]). Heterogeneity in site-specific IVE estimates was high (I2 = 63.4%) for A(H1N1)pdm09 in patients ≥65 years of age. IVE estimates for influenza B/Yamagata were homogenous (I2 = 0.0%).

Conclusions: These results, which were based on data collected from the GIHSN during the 2012-2013 influenza season, showed that influenza vaccines provided low to moderate protection against hospital admission with laboratory-confirmed influenza in adults targeted for influenza vaccination. In this population, IVE estimates against A(H1N1)pdm09 were sensitive to age group and study site. Influenza vaccination was moderately effective in preventing admissions with influenza B/Yamagata for all sites and age groups.

Publication types

  • Multicenter Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Female
  • Hospitalization / statistics & numerical data*
  • Humans
  • Influenza Vaccines / immunology*
  • Influenza, Human / epidemiology*
  • Influenza, Human / immunology*
  • Influenza, Human / prevention & control
  • Influenza, Human / virology
  • Internationality*
  • Male
  • Middle Aged
  • Seasons*
  • Sentinel Surveillance*
  • Treatment Outcome
  • Vaccination / statistics & numerical data
  • Young Adult


  • Influenza Vaccines

Grants and funding

The study was funded by a collaboration between CSISP (now FISABIO) in Valencia, Spain; INSERM and the French Vaccine Research Network (REIVAC) in France; the D.I. Ivanovsky Institute of Virology in Moscow, Russian Federation; the Research Institute of Influenza in St. Petersburg, Russian Federation; the National Influenza Reference Laboratory Capa-Istanbul, Turkey; and Sanofi Pasteur. Sanofi Pasteur participated in the design of the study but did not participate in the collection, management, analysis, or interpretation of the data, writing the manuscript, or the decision to submit the manuscript for publication.