title: Seasonal influenza vaccine effectiveness against influenza in 2012-2013: a hospital-based case-control study in Lithuania.
abstract: BACKGROUND
  Due to scarce information on seasonal influenza vaccine effectiveness (SIVE) against severe clinical influenza outcomes in risk populations, we conducted a case-control study to assess its effects against laboratory-confirmed influenza in hospitalized patients during the 2012-2013 influenza season.
  
  
  METHODS
  We conducted a test-negative case-control study among ≥18 years old patients with influenza-like illness (ILI) hospitalized in two Lithuanian hospitals. Cases were influenza A(H1N1), A(H3) or influenza B positive by RT-PCR, and controls were influenza negative. Additional demographic and clinical data to assess the role of confounding were collected. SIVE and its confidence intervals (95% CI) were estimated by using multivariate logistic regression as (1-OR)×100%.
  
  
  RESULTS
  The sample consisted of 185 subjects. Seasonal influenza vaccine uptake was 5%. Among 111 (60%) influenza positive cases, 24.3% were A(H1N1), 10.8% were A(H3) and 24.3% were influenza B cases. Unadjusted SIVE was 79% (95% CI -6% to 96%) and after the adjustment it increased to 86% (95% CI 19% to 97%).
  
  
  CONCLUSIONS
  Seasonal influenza vaccination in 2012-2013 was associated with reduced occurrence of laboratory-confirmed influenza, but due to low sample size the estimate of SIVE is imprecise. Given high prevalence of influenza in hospitalized ILI cases and low influenza vaccination coverage, there is a need to increase influenza vaccination rates.
authors.affiliation: Department of Pharmacy, Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), University of Groningen, A. Deusinglaan 1, P.O. Box XB45, 9713AV Groningen, The Netherlands; Department of Epidemiology, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, P.O. Box 30.001, FA40, 9700RB Groningen, The Netherlands. Electronic address: g.gefenaite@umcg.nl.
authors.forename: Giedre
authors.initials: G
authors.lastname: Gefenaite
authors.affiliation: Department of Medical Microbiology, Division of Clinical Virology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands.
authors.forename: Janette
authors.initials: J
authors.lastname: Rahamat-Langendoen
authors.affiliation: Department of Infectious, Chest Diseases, Dermatovenerology and Allergology, Vilnius University, Birutes str. 1, LT-08117 Vilnius, Lithuania.
authors.forename: Arvydas
authors.initials: A
authors.lastname: Ambrozaitis
authors.affiliation: Lithuanian University of Health Sciences, Department of Infectious Disease, Kaunas Clinical Hospital, Baltijos str. 120, LT-47116 Kaunas, Lithuania.
authors.forename: Aukse
authors.initials: A
authors.lastname: Mickiene
authors.affiliation: Department of Infectious, Chest Diseases, Dermatovenerology and Allergology, Vilnius University, Birutes str. 1, LT-08117 Vilnius, Lithuania.
authors.forename: Ligita
authors.initials: L
authors.lastname: Jancoriene
authors.affiliation: Lithuanian University of Health Sciences, Department of Infectious Disease, Kaunas Clinical Hospital, Baltijos str. 120, LT-47116 Kaunas, Lithuania.
authors.forename: Monika
authors.initials: M
authors.lastname: Kuliese
authors.affiliation: Lithuanian University of Health Sciences, Department of Infectious Disease, Kaunas Clinical Hospital, Baltijos str. 120, LT-47116 Kaunas, Lithuania.
authors.forename: Daiva
authors.initials: D
authors.lastname: Velyvyte
authors.affiliation: Department of Medical Microbiology, Division of Clinical Virology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands.
authors.forename: Hubert
authors.initials: H
authors.lastname: Niesters
authors.affiliation: Department of Epidemiology, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, P.O. Box 30.001, FA40, 9700RB Groningen, The Netherlands.
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Stolk
authors.affiliation: Institute of Public Health, Faculty of Medicine, Vilnius University, Ciurlionio str. 21/27, LT-03101 Vilnius, Lithuania.
authors.forename: Kestutis
authors.initials: K
authors.lastname: Zagminas
authors.affiliation: Department of Pharmacy, Unit of PharmacoEpidemiology & PharmacoEconomics (PE2), University of Groningen, A. Deusinglaan 1, P.O. Box XB45, 9713AV Groningen, The Netherlands; Department of Epidemiology, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, P.O. Box 30.001, FA40, 9700RB Groningen, The Netherlands.
authors.forename: Eelko
authors.initials: E
authors.lastname: Hak
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006761:Hospitals; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D009981:Influenza B virus; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D008097:Lithuania / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D014611:Vaccination / Q000706:statistics & numerical data
chemical_list: D007252:Influenza Vaccines
keywords: Case-control studies; Effectiveness; Influenza; Influenza vaccine; Lithuania