title: Vaccine effectiveness in preventing influenza hospitalizations in Navarre, Spain, 2010-2011: cohort and case-control study.
abstract: We evaluated the 2010-2011 seasonal influenza vaccine effectiveness in preventing hospitalizations. Using healthcare databases we defined the target population for vaccination in Navarre, Spain, consisting of 217,320 people with major chronic conditions or aged 60 years and older. All hospitalized patients with influenza-like illness (ILI) were swabbed for influenza testing. A total of 269 patients with ILI were hospitalized and 61 of them were found positive for influenza virus: 58 for A(H1N1)2009 and 3 for B virus. The incidence rates of hospitalization with laboratory-confirmed influenza were compared by vaccination status. In the Cox regression model adjusted for sex, age, children in the household, urban/rural residence, comorbidity, pandemic vaccination, pneumococcal vaccination, outpatient visits and hospitalization in the previous year, the seasonal vaccine effectiveness was 58% (95% CI: 16-79%). The nested test-negative case-control analysis gave an adjusted estimate of 59% (95% CI: 4-83%). These results suggest a moderate effect of the 2010-2011 seasonal influenza vaccine in preventing hospitalization in a risk population. The close estimates obtained in the cohort and the test-negative case-control analyses suggest good control of biases.
authors.affiliation: Instituto de Salud Pública de Navarra, Pamplona, Spain. jcastilc@navarra.es
authors.forename: Jesús
authors.initials: J
authors.lastname: Castilla
authors.forename: Víctor
authors.initials: V
authors.lastname: Martínez-Artola
authors.forename: Esther
authors.initials: E
authors.lastname: Salcedo
authors.forename: Iván
authors.initials: I
authors.lastname: Martínez-Baz
authors.forename: Manuel García
authors.initials: MG
authors.lastname: Cenoz
authors.forename: Marcela
authors.initials: M
authors.lastname: Guevara
authors.forename: Nerea
authors.initials: N
authors.lastname: Alvarez
authors.forename: Fátima
authors.initials: F
authors.lastname: Irisarri
authors.forename: Julio
authors.initials: J
authors.lastname: Morán
authors.forename: Aurelio
authors.initials: A
authors.lastname: Barricarte
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology
chemical_list: D007252:Influenza Vaccines