title: Methodological quality of systematic reviews on influenza vaccination.
abstract: BACKGROUND
  There is a growing body of evidence on the risks and benefits of influenza vaccination in various target groups. Systematic reviews are of particular importance for policy decisions. However, their methodological quality can vary considerably.
  
  
  OBJECTIVE
  To investigate the methodological quality of systematic reviews on influenza vaccination (efficacy, effectiveness, safety) and to identify influencing factors.
  
  
  METHODS
  A systematic literature search on systematic reviews on influenza vaccination was performed, using MEDLINE, EMBASE and three additional databases (1990-2013). Review characteristics were extracted and the methodological quality of the reviews was evaluated using the assessment of multiple systematic reviews (AMSTAR) tool. U-test, Kruskal-Wallis test, chi-square test, and multivariable linear regression analysis were used to assess the influence of review characteristics on AMSTAR-score.
  
  
  RESULTS
  Fourty-six systematic reviews fulfilled the inclusion criteria. Average methodological quality was high (median AMSTAR-score: 8), but variability was large (AMSTAR range: 0-11). Quality did not differ significantly according to vaccination target group. Cochrane reviews had higher methodological quality than non-Cochrane reviews (p=0.001). Detailed analysis showed that this was due to better study selection and data extraction, inclusion of unpublished studies, and better reporting of study characteristics (all p<0.05). In the adjusted analysis, no other factor, including industry sponsorship or journal impact factor had an influence on AMSTAR score.
  
  
  CONCLUSIONS
  Systematic reviews on influenza vaccination showed large differences regarding their methodological quality. Reviews conducted by the Cochrane collaboration were of higher quality than others. When using systematic reviews to guide the development of vaccination recommendations, the methodological quality of a review in addition to its content should be considered.
authors: Immunization Unit, Robert Koch Institute, Berlin, Germany.
authors: Cornelius
authors: C
authors: Remschmidt
authors: Immunization Unit, Robert Koch Institute, Berlin, Germany.
authors: Ole
authors: O
authors: Wichmann
authors: Immunization Unit, Robert Koch Institute, Berlin, Germany. Electronic address: HarderT@rki.de.
authors: Thomas
authors: T
authors: Harder
mesh_terms: D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human; D055811:Journal Impact Factor; D010506:Periodicals as Topic; D017594:Publication Bias; D012107:Research Design / Q000592:standards*; D012196:Review Literature as Topic; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines
keywords: AMSTAR; Influenza vaccination; Meta-analysis; Methodological quality; Quality appraisal tool; Systematic review