title: Selection bias in evaluating of influenza vaccine effectiveness: a lesson from an observational study of elderly nursing home residents.
abstract: Selection bias is of critical concern in the study of influenza vaccine effectiveness when using an observational study design. This bias is attributable to the inherently different characteristics between vaccinees and non-vaccinees. The differences, which are related both to vaccination and signs of clinical disease as an outcome, may lead to erroneous estimation of the effectiveness. In this report, we describe how selection bias among elderly nursing home residents may lead to a spurious interpretation of the protective effect of influenza vaccine. Our results should be a lesson in the importance of regarding selection bias when assessing influenza vaccine effectiveness.
authors.affiliation: Department of Public Health, Osaka City University Faculty of Medicine, 1-4-3, Asahi-machi, Osaka 545-8585, Japan. wakaba@med.osaka-cu.ac.jp
authors.forename: Wakaba
authors.initials: W
authors.lastname: Fukushima
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Yaichi
authors.initials: Y
authors.lastname: Mizuno
authors.forename: Kanzo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kase
authors.forename: Satoko
authors.initials: S
authors.lastname: Ohfuji
authors.forename: Megumi
authors.initials: M
authors.lastname: Fujieda
authors.forename: Akiko
authors.initials: A
authors.lastname: Maeda
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hirota
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D005260:Female; D006707:Homes for the Aged; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology*; D009981:Influenza B virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D009735:Nursing Homes; D012621:Seasons; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines