title: Estimating the influenza vaccine effectiveness against medically attended influenza in clinical settings: a hospital-based case-control study with a rapid diagnostic test in Japan.
abstract: BACKGROUND
  Influenza vaccine effectiveness (VE) studies are usually conducted by specialized agencies and require time and resources. The objective of this study was to estimate the influenza VE against medically attended influenza using a test-negative case-control design with rapid influenza diagnostic tests (RIDT) in a clinical setting.
  
  
  METHODS
  A prospective study was conducted at a community hospital in Nagasaki, western Japan during the 2010/11 influenza season. All outpatients aged 15 years and older with influenza-like illnesses (ILI) who had undergone RIDT were enrolled. A test-negative case-control design was applied to estimate the VEs: the cases were ILI patients with positive RIDT results and the controls were ILI patients with negative RIDT results. Information on patient characteristics, including vaccination histories, was collected using questionnaires and medical records.
  
  
  RESULTS
  Between December 2010 and April 2011, 526 ILI patients were tested with RIDT, and 476 were eligible for the analysis. The overall VE estimate against medically attended influenza was 47.6%, after adjusting for the patients' age groups, presence of chronic conditions, month of visit, and smoking and alcohol use. The seasonal influenza vaccine reduced the risk of medically attended influenza by 60.9% for patients less than 50 years of age, but a significant reduction was not observed for patients 50 years of age and older. A sensitivity analysis provided similar figures.
  
  
  CONCLUSIONS
  The test-negative case-control study using RIDT provided moderate influenza VE consistent with other reports. Utilizing the commonly used RIDT to estimate VE provides rapid assessment of VE; however, it may require validation with more specific endpoint.
authors: Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors: Motoi
authors: M
authors: Suzuki
authors: Hiroyuki
authors: H
authors: Yoshimine
authors: Yoshitaka
authors: Y
authors: Harada
authors: Naho
authors: N
authors: Tsuchiya
authors: Ikumi
authors: I
authors: Shimada
authors: Koya
authors: K
authors: Ariyoshi
authors: Kenichiro
authors: K
authors: Inoue
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D006764:Hospitals, Community; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D007251:Influenza, Human / Q000175:diagnosis / Q000517:prevention & control*; D007564:Japan; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D013997:Time Factors; D014611:Vaccination / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines