title: 2012-2013 Seasonal influenza vaccine effectiveness against influenza hospitalizations: results from the global influenza hospital surveillance network.
abstract: 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).
  
  
  RESULTS
  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.
authors.affiliation: Foundation for the Promotion of Health and Biomedical Research in the Valencia Region FISABIO - Public Health, Valencia, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Puig-Barberà
authors.affiliation: Foundation for the Promotion of Health and Biomedical Research in the Valencia Region FISABIO - Public Health, Valencia, Spain.
authors.forename: Angels
authors.initials: A
authors.lastname: Natividad-Sancho
authors.affiliation: Université Paris Descartes, Sorbonne Paris Cité, Inserm, CIC 1417 and the French Vaccine Research Network (REIVAC), Paris, France.
authors.forename: Odile
authors.initials: O
authors.lastname: Launay
authors.affiliation: D.I. Ivanovsky Institute of Virology, Moscow, Russian Federation.
authors.forename: Elena
authors.initials: E
authors.lastname: Burtseva
authors.affiliation: National Influenza Reference Laboratory Cappa-Istanbul, Istanbul, Turkey.
authors.forename: Meral A
authors.initials: MA
authors.lastname: Ciblak
authors.affiliation: Foundation for the Promotion of Health and Biomedical Research in the Valencia Region FISABIO - Public Health, Valencia, Spain.
authors.forename: Anita
authors.initials: A
authors.lastname: Tormos
authors.affiliation: Foundation for the Promotion of Health and Biomedical Research in the Valencia Region FISABIO - Public Health, Valencia, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Buigues-Vila
authors.affiliation: Foundation for the Promotion of Health and Biomedical Research in the Valencia Region FISABIO - Public Health, Valencia, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Martínez-Úbeda
authors.affiliation: Research Institute of Influenza, St. Petersburg, Russian Federation.
authors.forename: Anna
authors.initials: A
authors.lastname: Sominina
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control / Q000821:virology; D038622:Internationality; D008297:Male; D008875:Middle Aged; D012621:Seasons; D018571:Sentinel Surveillance; D016896:Treatment Outcome; D014611:Vaccination / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines