title: Relation of study quality, concordance, take home message, funding, and impact in studies of influenza vaccines: systematic review.
abstract: OBJECTIVE
  To explore the relation between study concordance, take home message, funding, and dissemination of comparative studies assessing the effects of influenza vaccines.
  
  
  METHODS
  Systematic review without meta-analysis.
  
  
  METHODS
  Search of the Cochrane Library, PubMed, Embase, and the web, without language restriction, for any studies comparing the effects of influenza vaccines against placebo or no intervention. Abstraction and assessment of quality of methods were carried out.
  
  
  RESULTS
  We identified 259 primary studies (274 datasets). Higher quality studies were significantly more likely to show concordance between data presented and conclusions (odds ratio 16.35, 95% confidence interval 4.24 to 63.04) and less likely to favour effectiveness of vaccines (0.04, 0.02 to 0.09). Government funded studies were less likely to have conclusions favouring the vaccines (0.45, 0.26 to 0.90). A higher mean journal impact factor was associated with complete or partial industry funding compared with government or private funding and no funding (differences between means 5.04). Study size was not associated with concordance, content of take home message, funding, and study quality. Higher citation index factor was associated with partial or complete industry funding. This was sensitive to the exclusion from the analysis of studies with undeclared funding.
  
  
  CONCLUSIONS
  Publication in prestigious journals is associated with partial or total industry funding, and this association is not explained by study quality or size.
authors.affiliation: Cochrane Vaccines Field, ASL (Azienda Sanitaria Locale) AL 20, 15100 Alessandria, Italy. jefferson.tom@gmail.com
authors.forename: T
authors.initials: T
authors.lastname: Jefferson
authors.forename: C
authors.initials: C
authors.lastname: Di Pietrantonj
authors.forename: M G
authors.initials: MG
authors.lastname: Debalini
authors.forename: A
authors.initials: A
authors.lastname: Rivetti
authors.forename: V
authors.initials: V
authors.lastname: Demicheli
mesh_terms: D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000517:prevention & control*; D033181:Information Dissemination; D055811:Journal Impact Factor; D016032:Randomized Controlled Trials as Topic / Q000191:economics / Q000592:standards*; D012109:Research Support as Topic
chemical_list: D007252:Influenza Vaccines